Liverpool manager Brendan Rodgers is being investigated about comments made about referee Lee Mason, the Football Association have confirmed.
The Northern Irishman labeled the performance of the match officials as "horrendous" as his charges fell to a disappointing 2-1 defeat at Manchester City on Thursday.
Rodgers' was particularly disappointed with the decision to disallow a goal from winger Raheem Sterling with the score still at 0-0, with replays showing the England international was in an onside position.
The 40-year-old also felt Luis Suarez should have had a penalty in the closing stages after tangling with Joleon Lescott.
Speaking after the game, Rodgers questioned the appointment of Mason who was born in Bolton, saying: "Hopefully we won't have a Greater Manchester referee with Liverpool-Manchester games in future."
The governing body must now decide whether Rodgers' comments "question the referee's integrity or imply bias".
Liverpool dropped to third in the Premier League as a result of the setback at the Etihad Stadium and faces a difficult trip to Chelsea on Sunday.