Liverpool risk expulsion from the Carabao Cup for fielding an ineligible player.
It is understood the matter relates to the involvement of Pedro Chirivella after he came on as a substitute during Wednesday’s third round win over MK Dons.
Chirivella, 22, spent the second half of last season on loan with Extremadura, meaning he required fresh international clearance to again play for the Reds.
The English Football League, which owns and operates the Carabao Cup, previously found Sunderland guilty of a similar offence in 2014.
Punishments range from financial penalties to possible expulsion from the competition. Liverpool are due to play a fourth round tie with Arsenal on October 30.
However Anfield officials insist that the issues surrounding Chirivella were caused by an administrative error, which will now be subjected to an EFL investigation.
“The club are aware of a potential administrative issue pertaining to one of our players,” read a club statement.
“We are working with the relevant authorities in order to establish the facts of the matter and will be making no further comment until this process is complete.”