The FA are contemplating whether to use a lip reader to investigate Jose Mourinho's touchline comments, according to Sky Sports.
Cameras caught Mourinho making comments following Saturday's dramatic 3-2 win over Newcastle United. It has been reported that some of those comments were swear words in Portuguese.
If the FA finds him guilty of using 'offensive, insulting or abusive language', Mourinho could receive a touchline ban for United's next match away at Chelsea.
Mourinho's position remains under scrutiny following United's poor start to the season. The Red Devils are currently eighth on the table having collected 13 points from 8 games.