(CNN) -- A shooting at a house party in Toronto killed two people and left 19 others wounded, many of the injuries a result of the ensuing commotion, authorities said Tuesday.
It's unclear what prompted the altercation that led to the shooting late Monday, Toronto Police Chief Bill Blair said.
The injured included an infant under age 3. The number of casualties is preliminary and may go up, according to authorities.
Blair described it as an unprecedented incident.
"The level of violence is something that we have never experienced and right now we're working very hard to ensure that we provide all the assistance that we can to the people who have been injured," he said. "We're working fully to identify the people responsible to get them off the street, to get their guns off the streets and bring them before the courts."
The incident comes six weeks after a mall shooting in the city killed one and injured seven others.
Of the eight casualties in the June shooting at Eaton Centre, seven suffered gunshot wounds. An additional woman was knocked down in the melee and suffered minor injuries.
CNN's Marina Landis and Umaro Djau contributed to this report.
™ & © 2012 Cable News Network, Inc., a Time Warner Company. All rights reserved.