Liverpool said it "utterly condemns" damage caused to Manchester United's team bus after a bottle was thrown as it made its way to Anfield on Sunday.
In a statement, the club said any fans found guilty of throwing objects would face serious consequences.
A video posted on social media shows a hand holding a glass bottle, then the word "go" being shouted before it is launched at the window of the coach.
Liverpool drew 0-0 with their arch-rivals in the Premier League encounter.
"Liverpool Football Club utterly condemns the actions that led to damage being caused to the Manchester United team bus during its arrival at Anfield this afternoon," the statement read.