Investigators from the FA spent several hours at the Kenilworth Road home of Luton Town FC, talking to club directors and employees, in an attempt to test the club’s compliance with transfer regulations.
The club’s former chairman Bill Tomlins previously admitted breaking the rules regarding payment to agents.
Investigators are now looking at the possibility that the club may be in breach of two serious rules.
The FA will not make any statement until the compliance team has finalised its report in relation to a total of eight transfers.
Mr Tomlins, whose ex-manager Mike Newell made claims about corruption in the game's transfer market, stood down in the wake of the FA inquiry.