The English Football League launched a formal investigation on Tuesday after Derby County complained that Leeds United manager Marcelo Bielsa sent a spy to the club's training ground last week.
The incident happened the day before the Championship clubs met at Elland Road, a game which Leeds won 2-0.
The EFL have now written to Leeds requesting their observations after the Yorkshire club apologised to Derby and reminded Bielsa of the club's principles of "integrity and honesty."
Following the victory over Derby that gave Leeds a four-point cushion at the top of the Championship standings, Bielsa admitted sending a member of his coaching staff to watch Derby train.
"The EFL has now determined that it is appropriate to consider this matter in the context of a number of EFL Regulations whilst also noting that the alleged actions appear to contravene the Club's Charter that all EFL Clubs agreed to in summer 2018," the EFL said in a statement.
The Football Association are already probing the incident and the EFL confirmed it will work with the governing body to ensure that any potential action taken "does not prejudice those investigations being undertaken."