The Latest on motorsport's busiest day, with Formula One's Monaco Grand Prix followed by the Indianapolis 500 and NASCAR's Coca-Cola 600 (all times local):
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3 p.m.
Takuma Sato slapped the wall at the Indy 500 - and may have saved Helio Castroneves.
Sato did not hit hard, but it was enough to bring out a much-needed caution for Castroneves with 37 laps remaining in the 100th edition. Castroneves had the right-rear portion of his wing hanging off and was close to getting black-flagged before the yellow came out instead.
The caution should allow Castroneves, who has led a big chunk of the race, to repair his wing for the final run to the finish.
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2:40 p.m.
More misfortune for the Andretti family at Indianapolis Motor Speedway.
This time, something so simple as tire pressure forced Marco Andretti off the pace and into the pits out of sequence, leaving him a lap down with a quarter of the race remaining in the 100th Indy 500.
Andretti started near the back but had climbed into the top 10 before his tires began showing a reading of too much pressure. He was almost 15 mph off the pace when he was forced to pit.
In more than 70 attempts, his family has only Mario Andretti's victory in 1969.
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2:25 p.m. ET
Another caution has caused more pit-road carnage at the Indy 500.
Andretti Autosport teammates Ryan Hunter-Reay and Townsend Bell, who had been near the front all day, collided in a chain-reaction that began when Bell struck Helio Castroneves leaving his stall.
Hunter-Reay, the 2014 champion, had significant damage to the front of his car.
Earlier in the race, Will Power bumped Tony Kanaan into the pit-road wall exiting his stall.
The caution leading to the latest trouble came out when Mikhail Aleshin got loose in the short-chute and spun into the wall. Conor Daly tried to avoid him and also spun toward the wall.
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2 p.m.
Sage Karam crashed hard during a battle for fifth place at the Indy 500.
Karam was on the outside of Townsend Bell and couldn't hold the line, sending him into the outside wall. Karam skidded several hundred feet along the barrier but stayed out of traffic.
Karam, who briefly led during pit stops, crashed on the first lap a year ago.
The young driver was back at an IndyCar race for the first time since a wreck at Pocono last year during which his car's nosecone bounced into Justin Wilson's cockpit. The impact killed the 37-year-old British driver.
Wilson's younger brother, Stefan Wilson, was also running in this year's Indy 500.
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1:45 p.m.
The defending champion is out of the Indianapolis 500.
Juan Pablo Montoya got sideways and hit the outside wall coming out of Turn 2, sliding back across the track before coming to rest on the grass. He was fortunate nobody else collided with him.
Montoya climbed out of his car and waved to fans that he was OK before climbing into an ambulance.
Juan Pablo Montoya says, ''I just got loose and I lost the car.'' The two-time winner says ''the thing just snapped.''
It was the lowlight of a rough start to the race for Penske Racing. Will Power and Simon Pagenaud were both penalized for early pit stops, shuffling them to the back of the field.
Penske is celebrating his 50th year in motorsports this year. So far, the party has been sour.
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1:15 p.m.
The first collision of the Indy 500 happened on pit road.
Tony Kanaan was in the fast, outer lane when Will Power was told it was ''all clear'' to exit his stall, and the two touched tires as Kanaan was forced into the wall. There did not appear to be any significant damage, but it's unclear whether Kanaan's steering will be affected.
Race stewards examined the incident and hit Power with a stop-and-go penalty.
The first caution of the race, which triggered the pit stops, was for debris on the track. Oriol Servia was also penalized for being too fast exiting pit lane.
James Hinchcliffe and Ryan Hunter-Reay spent much of the first 60 laps swapping the lead.
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1 p.m.
Townsend Bell is an intriguing dark horse in the Indy 500.
In the fifth car for Andretti Autosport, Bell started a surprising fourth and had moved into the lead by the quarter-point in the 100th running - not bad for a journeyman driver who signed on late and didn't even meet his spotters until he arrived this month.
Bell is in his 10th Indy 500, and he had a career-best fourth for KV Racing Technology in 2009. But he has not finished in the top 10 in the past three races, each with a different team.
None of those teams was Andretti, though. He has a hotrod under him for the Indy 500.
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12:50 p.m.
Ryan Hunter-Reay and James Hinchcliffe led the first round of green-flag pit stops in the Indy 500.
Both of them are in Hondas, and there was some question whether they would have better fuel mileage than Chevrolet. Hard to tell at this point because they also spent time out front, rather than in the draft, and punching through the air caused them to burn more fuel.
The early stops gave the lead to Josef Newgarden, the first time he'd been in front at the Indy 500.
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12:45 p.m.
The start of the 100th Indianapolis 500 was the cleanest in recent years, every driver settling their nerves during what is always a tense few laps around the historic speedway. James Hinchcliffe may have been the most nervous as he led the field to green, but he remained on point through the first dozen laps.
Former winner Buddy Lazier missed the start of the race with mechanical trouble. His team struggled to find speed in Indy all month and he pulled into the pits during the parade lap.
The weather couldn't be better at Indianapolis. The temperature is tipping into the 80s with just enough cloud cover to provide some relief from the sun for the 350,000 people on site for centennial running of ''The Greatest Spectacle in Racing.''
The sellout allowed the race to be televised locally for the first time in years.
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11:30 a.m.
Michael Andretti would love to be in tears at the end of this year's Indy 500.
After so many years of heartache for his family, Andretti is hopeful that his son Marco can finally end their long dry spell. Along with Mario Andretti, the three generations have made more than 70 starts in ''The Greatest Spectacle in Racing'' and have just one win to show for it - Mario's in 1969.
''I can't put it in words,'' Michael Andretti said as Marco's car was being pulled onto the starting grid. ''It may be the first time you ever see me cry. It would mean that much.''
Marco has his work cut out for him, starting in the middle of row five.
''If we get it done,'' Michael Andretti said, ''if he gets it done, it would be incredible.''
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11:15 a.m.
Indy 500 pole sitter James Hinchcliffe took a moment before the start of Sunday's race to send his best wishes to Andrew Palmer, a sports car driver who was involved in a serious wreck on Saturday.
The Bentley Team Absolute driver crashed during the Pirelli World Challenge race at Lime Rock Park, and Palmer's team said ''he has sustained a head injury and is being closely monitored.''
Hinchcliffe was involved in his own serious crash during practice before last year's Indy 500. He sustained a serious concussion and his leg was impaled by a piece of his suspension, which nearly caused him to bleed to death. It took a team of trauma physicians to save his life.
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10:35 a.m.
There are plenty of celebs walking the red carpet in the shadow of the famed pagoda at Indianapolis, including ''Star Trek'' star Chris Pine, rapper Ice-T and Nick Gehlfuss of ''Chicago Med.''
Lady Gaga was also at the speedway for the 100th running of the Indy 500, though she kept a very low profile, dressed down in jean shorts with her hair pulled back in a tight ponytail.
IndyCar CEO Mark Miles took a helicopter ride above the speedway hours before the start of the 500 and marveled at the crowd ''pouring in.''
Miles also met with a handful of NASCAR executives who flew to Indianapolis early Sunday to experience the 100th running before they headed back to North Carolina for the Coca-Cola 600.
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10: 20 a.m.
The Indianapolis Children's Choir was tabbed to sing ''God Bless America'' before Darius Rucker performed the national anthem for the 100th running of the Indianapolis 500. The sun-splashed day of pageantry also included an F-18 flyover and Josh Kauffman joining the children's choir in singing ''Back Home Again in Indiana.''
The grand marshal is actress Florence Henderson, who told drivers it's time to go to their cars, and Indianapolis Motor Speedway matriarch Mari Hulman George gave the command for drivers to start their engines. Roger Penske was behind of the wheel of the pace car.
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4 p.m.
Defending Formula One champion Lewis Hamilton has won the Monaco Grand Prix, holding off Daniel Ricciardo for his first win of the season.
Hamilton had not won for the past eight races, but he pulled ahead after Ricciardo came in on lap 33 for ultra-soft tires only to have his Red Bull pit crew not ready. It cost him valuable time and he came out behind Hamilton.
Ricciardo was close to overtaking Hamilton on lap 37. But Hamilton held his line at the Mirabeau turn, prompting an angry reaction from Ricciardo, who waved his hand furiously as he was forced to back off.
Mexican driver Sergio Perez of Force India was third ahead of Sebastian Vettel's Ferrari.
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3:30 p.m.
The wrecks continue at the Monaco Grand Prix, this time with Sauber teammates Felipe Nasr and Marcus Ericsson getting into each other.
Nasr received team orders to let Ericsson through but apparently ignored them. A determined Ericsson went for a gap that simply did not exist and they both collided at the Rascasse turn.
Ericcson quipped that his teammate's radio ''musn't be working.''
In all, seven drivers were knocked out of the race. They included Red Bull's Max Verstappen, who became the youngest winner of an F1 race at the Spanish GP two weeks ago.
On a day with slippery conditions on the track, the 18-year-old slammed into a barrier at the same point where he crashed in Saturday's third and final practice.
Russian driver Daniil Kvyat got into the turn at La Rascasse, taking Kevin Magnussen into the barriers with him. Kvyat, who has twice been blamed for racing incidents with Ferrari driver Sebastian Vettel this season, went out of the race.
Ferrari driver Kimi Raikkonen and British driver Jolyon Palmer - Magnussen's teammate at Renault - both crashed earlier.
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2:30 p.m.
After seven laps behind a safety car, British driver Jolyon Palmer crashed out and was soon joined back in the garage by Ferrari driver Kimi Raikkonen.
Raikkonen lost control of his car after breaking too late going into a hairpin, locked his wheels and slammed into the barrier.
He tried to continue but almost caused another collision, with French driver having to brake sharply to avoid smashing into the back of him.
''What's Kimi doing?'' screeched Grosjean.
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1:25 p.m.
The Monaco Grand Prix traditionally sees an influx of movie stars from nearby Cannes, where the famous film festival is held.
This year, the events are a week apart and there's a notable absence of big names so far.
However, actor Patrick Dempsey - a long-time star of ''Grey's Anatomy'' and a huge motorsport fan - is in the paddock.
The 50-year-old American has been chatting with Red Bull driver Max Verstappen and Frenchman Romain Grosjean - who drives for the American-based Haas team - before the race.
There is more of a sporting flavor than a Hollywood theme, with basketball stars Chris Bosh (Miami Heat) and Tony Parker (San Antonio Spurs) and International Olympic Committee president Thomas Bach all present.
Bosh has expressed his support for Lewis Hamilton. Arsenal soccer star Theo Walcott and Danish tennis player Caroline Wozniacki are also here.
