An investigation has been launched by the Rugby Football Union (RFU) and Bath amid reports a supporter confronted referee Chris Garner following Friday's defeat to Saracens.
Garner had earlier sent off Bath's Anthony Watson for what the official deemed a dangerous tackle on the back's England team-mate Alex Goode in a contentious fixture at the Rec, which Premiership leaders Sarries won 30-10.
Following the match it was reported a Bath fan entered Garner's changing room to remonstrate with the official.
An RFU spokesperson subsequently told Omnisport: "I can confirm that we are investigating [the incident]."
A Bath statement added: "Bath Rugby are aware of an incident involving the match officials which took place after the game against Saracens.
"In conjunction with the RFU and Premiership Rugby, the club is currently investigating the incident and will ensure appropriate action is taken."
Watson was left fuming by the red card and appeared to argue with Sarries' Chris Ashton - who scored twice on his return from a 10-week ban - on his way off the pitch.
Bath coach Mike Ford commented on the decision after the match, saying: "By the letter of the law, it is a sending off, isn't it? He got underneath Alex, and Alex landed awkwardly.
"You get underneath the guy jumping, take his legs away and he lands awkwardly like he did, it's a red. Anthony is gutted.
"He was going for the ball, Ashton checked his run, and then all of a sudden he is underneath the player. It was an accident. We will have a look at it. We will fight his corner."