Ravel Morrison scored two goals in United's 3-2 victory at Anfield
Liverpool and Manchester United's young players were involved in a tempestuous FA Youth Cup tie at Anfield on Sunday.
Both sides had two men sent off, while three United fans were arrested and six ejected during the quarter-final match.
United won 3-2 but Liverpool's Stephen Sama and Conor Coady and United's Paul Pogba and Tyler Blackett saw red.
Police took action against the United supporters after they reportedly set off a flare and sang songs about the Hillsborough and Heysel disasters.
United manager Sir Alex Ferguson was watching from the stands as the Reds took a 2-0 lead courtesy of strikes either side of half-time by Adam Morgan.
But the controversy started when Liverpool had defender Sama dismissed for a challenge on midfielder Ryan Tunnicliffe in the penalty area.
the midfielder signed in acrimonious circumstances from French side Le Havre
in 2009, scored from the spot but was shown a second yellow card by referee David Coote for stopping midway through his run-up.
Winger Larnell Cole scored the retaken penalty before a double from highly rated forward Ravel Morrison put United 3-2 ahead.
United left-back Blackett and Liverpool captain Coady then came together in an off-the-ball clash which left the latter with a bloodied nose and saw both players dismissed.
The Red Devils' victory in front of a 12,000 crowd came a week after
their 3-1 Premier League defeat
by Liverpool at the same ground.
That match was marred by confrontations between the two sets of players following challenges by Liverpool's Jamie Carragher on Nani and United's Rafael da Silva on Lucas.