The English Football League (EFL) is investigating Liverpool to find out if the Premier League club potentially fielded an ineligible player in their third round Carabao Cup victory over Milton Keynes Dons on Wednesday.
Possible sanctions could include a fine or Liverpool being removed from the competition. The identity of the player in question was not disclosed.
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"We are currently considering the matter," an EFL spokesman said.
Liverpool beat League One side MK Dons 2-0 to set up a fourth round clash with Arsenal at the Emirates Stadium.
Liverpool manager Jurgen Klopp fielded four teenagers in the starting line-up for the third round clash.
"The club are aware of a potential administrative issue pertaining to one of our players," a Liverpool spokesman said.
"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."