Liverpool manager Brendan Rodgers has been asked for "his observations" following his recent comments about referee Lee Mason, the Football Association has confirmed.
Rodgers questioned the decision to appoint Mason to his side's Boxing Day Barclays Premier League defeat at Manchester City because he is from the Greater Manchester area.
The Reds boss had been frustrated by a number of decisions made by Bolton official Mason and his assistants during the 2-1 loss at the Etihad Stadium.
An FA spokesman said: "We have contacted Brendan Rodgers to seek his observations in relation to his post-match comments made following the game at Manchester City."
Rodgers has until January 2 to respond to the FA's request.
The FA will then consider whether any further action is necessary.
Rodgers could be warned as to his future conduct or hit with a financial penalty if found guilty of any charge.