The Dutch Football Association (KNVB) are looking into Chelsea's signing of highly-rated teenager Nathan Ake.
It emerged before Christmas that the Blues had agreed a deal to bring in the centre-back, who has come through the youth ranks at Feyenoord.
However, the move has sparked controversy as Ake is still only 15 and there are strict rules in Holland against players having agents until they are 16.
The role played by agent Dan Kramp of the Forza Fides agency has therefore come under scrutiny, with reports suggesting he took Ake to London over the festive period to finalise the transfer.
Dutch PFA spokesman Danny Hesp said in The Sun: "The rules clearly state that agents can't do anything with children under 16.
"Yet this agent turns up with a 15-year-old at Chelsea so the FA has got to tackle this issue."
The KNVB has confirmed the matter will now be investigated, with Ake set to turn 16 on Friday.
A spokesman said: "It's a transfer involving a player who is not yet 16 so our integrity unit is going to take a look at it."
Chelsea have responded by saying they worked closely with Feyenoord throughout the negotiations, insisting their dealings with the Dutch club were above board.
A Blues spokesman said: "We've kept Feyenoord abreast of our interest from the very beginning and as a result have agreed terms with the club for the player's transfer to Chelsea in July."
