A casual game of hockey at the MTS Iceplex in Winnipeg turned violent Thursday night when a player attacked a referee, knocking him out, witnesses told CBC News.

Paramedics were called and the ref was taken to hospital immobilized on a stretcher some time after 10 p.m. CT.

Witnesses said the player received a penalty and was being escorted to the box when he punched the official and then kicked him in the head.

Another player said the recreational game had been going smoothly up until that point, and his teammates had remarked that it was one of the least aggressive games they played all year.

Police are looking into the incident and whether alcohol was a factor.

"We will enter into an investigation if we can substantiate charges, and victims and so forth want to pursue those charges," Const. Jason Michalyshen of the Winnipeg Police Service said.

Hockey Winnipeg warned minor-level coaches back in March that attacks on referees were reaching epidemic levels. Officials were being pushed, punched and bitten, particularly in games involving players aged 15 to 19, but also at younger ages.

At the time, Hockey Manitoba was reviewing 16 serious cases of players or coaches abusing officials.