Manchester United's 1-0 Premier League Under-21 victory against Liverpool on Monday night was interrupted by a pitch invader and a flare being thrown onto the pitch.
The game, which involved a number of first-team players on both sides, took place at Langtree Park, the home of rugby league side St Helens and was decided by Italian defender Michele Fornasier's goal in added time at the end of the match.
Alex Buttner and Nick Powell turned out for United, while Raheem Sterling, Suso, Andre Wisdom and Jonjo Shelvey were named in a strong Liverpool side which had Stephen Sama sent off early in the second half for a second yellow card.
Liverpool striker Adam Morgan, 18, was confronted by the pitch invader as a sizeable crowd watching the north-west rivals threatened to spill over.
Two years ago a fiery FA Youth Cup game at Anfield, which saw both sides finish with nine men, was marred by songs about the Hillsborough and Heysel disasters. Three arrests were made for drunkenness and six United supporters were ejected.