The Football Association (FA) has asked Jurgen Klopp to explain his comments about referee Kevin Friend following Liverpool's draw with West Ham.
The Premier League leaders went ahead at London Stadium on Monday through a Sadio Mane goal, with the officials failing to penalise James Milner for a clear offside in the build-up.
Klopp suggested Friend favoured the home side in 50-50 decisions after half-time, as the Reds went on to draw for the second game in a row thanks to Michail Antonio's equaliser.
Speaking to Sky Sports, the Liverpool manager said: "There were so many situations where it was 50-50 or 60-40... [he gave a] free-kick for the other team. As a human being, I know if I make a big mistake in the first half, I don't want to open the gap even more."
Omnisport understands the FA has asked Klopp to provide written observations following his remarks.
Managers are allowed to speak about referees after matches, provided they do not insinuate bias, call their integrity into question or say anything offensive.
Liverpool's draw moved them three points clear of Manchester City at the top of the table, with the champions set to snatch the lead if they beat Everton on Wednesday.
