A man was in critical condition in hospital on Monday, after he fell off the roof of a moving SUV on St-Jean Boulevard in Dollard. (CBC)

Montreal police were asking for help from local businesses on Monday to track down an SUV involved in an apparent car-surfing stunt.

The incident happened at around 3 a.m. ET Monday on St-Jean Boulevard near the corner of Ernest Street, in Dollard-des-Ormeaux. A man believed to be in his 20s apparently fell from the roof of a dark SUV.

Police said the vehicle was stopped at a red light, and when the light changed to green, the SUV started moving and the man, who was "car-surfing" atop the vehicle, lost his balance. He was brought to hospital and remained in critical condition on Monday.

Montreal police spokesman Olivier Lapointe called the incident a dangerous stunt and said police are considering it a hit-and-run.

“We're going door-to-door to every store that has surveillance cameras to try to get pictures of the truck, and possibly the people inside of it," Lapointe said. "So far we’ve been able to talk to witnesses, people who were at the same intersection where that happened, but they gave us very little description of the truck."

Police weren’t able to identify the man Monday morning but hope his fingerprints would be able to help.