But a spokesman says it's unclear whether the teen heartthrob himself is accused in the attack or simply one of his companions.
Const. Victor Kwong says officers were called either late Sunday or early Monday to the area of Dundas Street West and University Avenue.
But he says little else is known about the incident because investigators are still questioning witnesses.
Bieber, 19, was seen at the Air Canada Centre during Sunday's hockey game.
Kwong says he believes the young star was in the limo at the time of the alleged attack.
"But whether he's the guy who did the actual assaulting, I don't know," he said.
Also on HuffPost