An FA Youth Cup tie between Liverpool and Manchester United at Anfield saw four red cards and several fans arrested amid ugly scenes.
United fans sang songs about Heysel and Hillsborough tragedies of the 1980s that saw the deaths of 135 people. Three fans were arrested and six ejected from the ground.
A United spokesman said: "Singing songs about the Hillsborough and Heysel tragedies is disgraceful. We will deal harshly with anyone brought to our attention."
Former Liverpool striker John Aldridge, present during the Hillsborough disaster of 1989, said he was horrified by the behaviour of the fans on Sunday.
"I have never seen anything like that before at a youth game and I never want to see anything like it again," he told the Liverpool Echo. "It was disgusting.