Burnley have condemned "tragedy chanting" that took place during their 1-1 draw against Manchester United at Old Trafford.
The Clarets, who are second-bottom in the Premier League, scored a late equaliser on Saturday to grab a vital point.
But following the match the club issued a statement after "offensive footage" was posted online showing offensive "gesturing and chanting" in the away end.
"We are aware of offensive footage currently circulating on social media from the away end of today’s fixture at Old Trafford," the club said.
"Tragedy related gesturing and chanting is completely unacceptable, and Burnley Football Club take a zero-tolerance approach.
"We will continue to work with Greater Manchester Police, Lancashire Police and Manchester United to help identify and prosecute the individuals responsible."
Last month two men were arrested on suspicion of tragedy chanting during the Manchester United v Liverpool FA Cup match at Old Trafford.