MONTREAL - Quebec's bureau of independent investigations (BEI) is investigating after a man fell two storeys and was critically injured during a police operation on Wednesday.

The incident happened as Montreal police attempted to arrest the 23-year-old-man just before 7 p.m. near Sherbrooke and Messier streets, according to preliminary information from the BEI.

Pursued by officers, the bureau says the young man fled into a nearby building and jumped either out a window or off a balcony, falling two storeys. He was injured by the fall, the BEI reports, but he continued to run from police.

Montreal police officers intercepted the man shortly after and arrested him, but he fell unconscious, the BEI said. He was transported to the hospital, where his condition is considered critical.

Eight BEI investigators will look into the incident with the assistance of Quebec provincial police, who will provide two forensic technicians to work under BEI supervision.

The BEI takes over cases when a person is injured during a police operation. It is asking witnesses to reach out via their website.