FIFA has confirmed to ESPN FC that Liverpool have been in contact with governing body over the eligibility of defender Joel Matip.
Liverpool were forced to withdraw Matip from selection ahead of Sunday's 1-1 draw with Manchester United as the club claimed they had failed to receive clear guidance from FIFA as to whether the Cameroon defender can play while the African Nations Cup takes place.
Matip was one of seven players who rejected the chance to join up with Cameroon at the tournament in Gabon, with the Cameroon Football Federation saying it "reserves the right to take action against these players in line with FIFA regulations."
A FIFA spokesperson has told ESPN FC that it directed Liverpool to the provisions of its Regulations on the Status and Transfers of Players.
"We can confirm that Liverpool FC contacted FIFA about the matter to which you refer," the spokesperson said. "Our services answered by directing the club to the applicable provisions [Annexe 1 of the Regulations on the Status and Transfer of Players] in particular its art.5."
Article five of Annexe 1 on the release of players to association teams reads as follows: "A player who has been called up by his association for one of its representative teams is, unless otherwise agreed by the relevant association, not entitled to play for the club with which he is registered during the period for which he has been released or should have been released pursuant to the provisions of this annexe, plus an additional period of five days."
The FIFA spokesperson also indicated that any potential violations of the rules would need to be investigated by FIFA Disciplinary Committee but offered no indication whether Matip was eligible or not.
Liverpool consider Matip to be retired from international football, as he has not played for his country since September 2015.
Back in December, sources told ESPN FC that Matip held talks with Cameroon boss Hugo Broos, who tried to convince the defender to end his international exile.
Cameroon included Matip in their 35-man provisional squad for the tournament in the hope of a sudden U-turn, before they later left him out of the 23-man squad for the Nations Cup.
The Cameroon Football Federation did not respond to ESPN FC's requests for comment.