Manchester United's team bus suffered a broken window due to a thrown bottle.
The Red Devils were arriving at Anfield for their Premier League game against Liverpool on Sunday.
While the 0-0 draw went off without a hitch, United's players did get a scare pre-game when the window broke.
Per PA, fans were chanting the song "Oh Manchester, is full of s***" as the bus went by.
Liverpool issued a statement post-game, stating: 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.
We are aware of footage of the incident circulating online and are working with Merseyside Police, to fully investigate and identify those responsible. Any individuals found guilty of this reprehensible behavior will also face the full force of the club's sanction process."