Newcastle boss Joe Kinnear described referee Martin Atkinson as a "Mickey Mouse" official following Toon's defeat at Fulham. The temporary Newcastle chief could now face an FA charge after being asked to explain his comments.
Football Association disciplinary chiefs have written to the 61-year-old, who has a week to respond, and then a decision will be taken on whether or not further action is required.
An FA spokesman said: "The FA have confirmed they have written to Joe Kinnear to ask him to explain his comments about referee Martin Atkinson following the game at Fulham."