A man died Tuesday after police used a Taser to subdue him, in what is believed to be the first such case in Winnipeg.

Witnesses told CTV Winnipeg the unidentified man, reportedly in his 20s, had been wielding a knife. But police spokesperson Const. Jacqueline Chaput would not confirm that report.

She said the "electronic control device" was used during a police call to a person's home, but would not give specific details.

"Upon attending, officers encountered a male at the rear of a residence," she said. "This resulted in an officer deploying his electronic control device. The male was conveyed to hospital in critical condition and has since succumbed to his injuries."

It's unclear why the man died or why officers were forced to use a Taser. But Chaput said the confrontation was serious enough that more than five police officers were dispatched to the scene.

Witnesses say police and paramedics tried to revive the man before he was taken to hospital, where he was pronounced dead.

Chaput said the homicide unit is investigating the incident because it involved a police officer.

Police told CTV News Tuesday night they are still trying to determine the identity of the man.

Witnesses said they saw police chasing the man, who was wearing jeans and a white T-shirt, and that the man then jumped over a fence.

"The next thing we know is that a witness who lives on the street and whose house is on the back lane where the Tasering occurred heard a loud siren," reported CTV's Murray Oliver in Winnipeg. "She peeked around the corner and saw police trying to revive a man who was prone on the ground."

Taser deaths around the country raise concerns

Several provincial and national probes were launched into Taser use after several high-profile deaths allegedly involving the devices.

A public inquiry into the death of Polish immigrant Robert Dziekanski will take place this fall. Dziekanski had been waiting for several hours at Vancouver International Airport last fall when he became agitated. He died after being shocked with a Taser gun and subdued by four RCMP officers.

Following a scathing report on Taser use by RCMP Public Complaints Commissioner Paul Kennedy, the RCMP pledged to restrict use of the devices and give officers clearer guidelines.

Nova Scotia's government also issued new restrictions earlier this month aimed at ensuring stun devices are used appropriately.

With reports from CTV Winnipeg and files from The Canadian Press