FIFA and Nigeria's soccer federation are investigating Argentina's 4-1 loss in Nigeria on Wednesday after betting patterns suggested it was targeted by match fixers.
It is the highest profile match yet in a wave of suspicious recent international exhibitions, often with goals scored from penalty kicks.
The match ''was one that we had an active interest in, and forms part of a wider ongoing FIFA investigation,'' soccer's world governing body said Saturday.
FIFA was ''working closely'' with its betting monitoring agency, Early Warning System, which tracks wagers placed with more than 400 operators worldwide.
A second-string Argentina team was outplayed by Nigeria, which earned its first victory over the South Americans in a one-sided match.
The Nigeria Football Federation, which organized the match, said it would help FIFA's investigation and also set up its own inquiry, but denied any knowledge of match fixing, stressing it was ''unaware of any suspicious motives in this game.''
''We will put all these measures (the inquiry) in place in the spirit of fair play and transparency,'' NFF General Secretary Musa Amadu said in a statement. ''But we would still insist that, until it is proven beyond doubt, we believe that we won this match fair and square ... There remains, to the best of our knowledge, no untoward motives to this game than to play it fairly and win it fairly.''
Argentina coach Sergio Batista, talking Saturday at a press conference in Warsaw ahead of his team's exhibition against Poland on Sunday, said he ''did not notice anything alarming'' during the Nigeria match.
Hours before kick-off at the National Stadium in Abuja on Wednesday, FIFA President Sepp Blatter launched his ''Zero Tolerance'' campaign to stop corruption in soccer.
FIFA's 208 member nations in Zurich also passed new rules to control the organization of international matches, including the power to veto referee appointments.
Referee Ibrahim Chaibou of Niger awarded two penalties - one to each side - in Wednesday's game between two teams who played each other at the 2010 World Cup in South Africa.
Nigeria took a 2-0 lead with a 26th minute spot-kick after Chaibou awarded a foul against Argentina defender Federico Fazio.
Five minutes of stoppage time were announced at the end of the match, with play continuing until the 98th minute, when Argentina scored with a penalty kick from Mauro Boselli.
Argentina's spot kick was awarded by Chaibou for a debatable handball after the ball appeared to strike a Nigerian defender on the shin and then bounce up and hit a teammate on the thigh.
Argentina fielded a below-strength lineup without star forwards such as Lionel Messi, Gonzalo Higuain and Angel di Maria.
However, there was no suggestion that players from either team were involved in manipulating the match.
Chaibou is one of the most experienced FIFA-approved referees with 15 years' service on the international list. He was born in 1966 and must step down this year on reaching FIFA's referee age limit of 45.
As match-fixing investigations develop across the world, FIFA announced last month it would pay Interpol $29 million over the next 10 years to educate referees, players, coaches and officials in how to resist corruption.
''FIFA is currently receiving lots of information and cooperation across Europe, Asia, Africa and South and Central America, and as an organization we are committed to tackling this problem in the most vigorous way possible,'' the governing body said.
