The Football League have confirmed they are investigating Leeds United over the recent "Spygate" scandal.
The EFL say the decision to formally investigate the matter is a result of the admission by Leeds head coach Marcelo Bielsa that he sent an individual to watch Derby train ahead of the match between the teams last Friday.
Derbyshire Police were forced to intervene and move the individual on but he was not arrested.
Leeds have since apologised to Derby and said they will remind Bielsa of his responsibilities.
Bielsa insisted the practice was not unlawful or illegal, but he could still fall foul of EFL regulations which state clubs must behave towards each other in good faith.