Deadman has been accused by Shrimpers fans of raising two fingers in their direction while appearing to rub the back of his head during Southend's goalless draw at Fleetwood in League Two on Saturday.
The alleged incident at the Highbury Stadium came midway through the first half while the match official was standing over striker Britt Assombalonga as he received treatment from the club's physio.
The FA have confirmed to Press Association Sport they are making inquiries as they investigate the matter further.
Lancashire Police have stated they were made aware of the incident but insist it is not a police matter, with Southend also leaving it in the hands of the authorities.
