LONDON — Premier League referee Mark Halsey has asked police to investigate abusive comments about him on Twitter after officiating in the heated match between Liverpool and Manchester United. The insulting online messages Monday referenced Halsey's battle with throat cancer in 2009. Halsey made two contentious decisions in United's 2-1 victory at Anfield Sunday that went in favor of the visitors. Halsey returned to refereeing in March 2010 following his cancer battle. No Premier League referees have Twitter accounts, according to the body that oversees match officials in England. — AP