Liverpool are the subject of an EFL investigation into whether they fielded an ineligible player during their Carabao Cup third round win over MK Dons.
The EFL have launched an enquiry over claims that the Reds breached rules in using Pedro Chirivella as a second-half substitute at Stadium MK on Wednesday.
Chirivella spent the second half of last season on loan at Spanish second-tier side Extremadura UD but failed to make an appearance due, reportedly, to missing the deadline to register.
The 22-year-old is understood to have required clearance to play for Liverpool upon his return, with the club now facing the axe from the competition with Arsenal currently their scheduled opponents in the fourth round.
Liverpool said in a statement: "The club are aware of a potential administrative issue pertaining to one of our players.
"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."
Chirivella's substitute appearance on Wednesday was only his third ever appearance for Liverpool, his last coming in May 2016.
