The game’s governing body are looking into potential misdemeanours by the club for a third time in the past eight years but a swift conclusion is not expected.
Their probe centres on the acquisition of foreign players under the age of 18, although it has not been revealed what deals are subject of concern.
Strict rules have been put in place to help protect smaller clubs from having their best talent being prised away. Chelsea have already fallen foul of Fifa over the transfer of Gael Kakuta from Lens in 2007.
The French club complained over the manner in which he was lured away to Stamford Bridge at the age of 16 when he was still under contract.
Chelsea were banned by Fifa in 2009 from signing players for two transfer windows, however that punishment was overturned on appeal to the Court of Arbitration for Sport although the club were fined.
The Blues also came under scrutiny when it emerged that Burkina Faso international Bertrand Traore had played for the club in a reserve game at Arsenal at the age of 16 before he had been given clearance for his country.
But Chelsea always protested their innocence and it was decided there was no case to answer.
La Liga clubs Real Madrid and Atletico Madrid have both been punished heavily by FIFA over rule breaches.
In Pictures | Chelsea vs Arsenal | 17/09/2017
Atletico were banned from signing players for the past two windows over misconduct regarding the purchase of young talent.
Their appeal to CAS was turned down and the decision has played a part in their struggle to sign Diego Costa from Chelsea.
Meanwhile, Real were initially handed the same punishment last year, although were able to get the ban on signing players reduced to just one window.
FIFA refused to comment on what business activity they are looking into but said there is no deadline for the investigation to be competed.
It is believed Chelsea’s case is not as serious as that which led to the two Spanish clubs being punished.
A FIFA spokesman said: “As the investigation is ongoing no further comment is possible.”
Chelsea were not able to be contacted this morning but a spokesman said last night: “Chelsea FC complies with all FIFA statutes and regulations when recruiting players.”
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