Brentford are set to investigate an altercation between Crawley Town defender Paul Connolly and a Bees supporter near the end of the game at Griffin Park on Tuesday night.
The club say they will look at footage of the incident, which appears to show Connolly hitting out at the fan.
“It does look as though the ball went into the crowd, and from what I could see it was thrown towards the player,” said Brentford chief executive Mark Devlin.
“He didn’t like it and there appeared to be an exchange, whether it was a slap or a punch or whatever.
“The referee has moved in and a plastic bottle has come onto the pitch, so no doubt we’ll hear from the Football League about that as well.
“The club will wait to see what the police say and then take it up with Crawley. If the Football League ask us for our input we will investigate it and let them know from our point of view what’s gone on.”
Brentford won the match 1-0 to move a step closer to promotion from League One.