A man is dead after a dam released a flood of water onto the Capilano River Thursday afternoon.

Witnesses told CTV News they watched as a wall of water came rushing down the river at around 2 p.m.

North Vancouver RCMP said five people were swept away, and that one of them was killed.

"It's a very unfortunate and sad occasion," Sgt. Peter DeVries said at a late news conference. "This will be a really difficult time for this person's family and friends and loved ones, and our hearts really do go out to them."

Video from the Cleveland Dam malfunction today in North Vancouver @GlobalBC @CTVVancouver @CBCVancouver I was walking my dogs there just before 2pm pic.twitter.com/Edsf6wqmWB

— Christine Tam (@christinetam) October 2, 2020

Authorities have not released the victim's name as they're still working to notify his next of kin, DeVries said. The man's death is being investigated by the BC Coroners Service.

There's no indication that anyone else was caught in the sudden rush of water, but DeVries said emergency responders would be scouring the river in case there were additional victims.

The RCMP said most, if not all, of the people who were swept away had been fishing. Authorities haven't determined whether they were in the water or at the shore, and whether anyone was wearing a personal flotation device.

DeVries urged anyone who uses the fast-flowing river to wear a flotation device, but stressed that he wasn't suggesting that was a factor in Thursday's tragedy.

Nick Nouri, who lives in the area, told CTV News the rushing water caught the anglers completely off-guard.

"It happened so fast, so sudden," Nouri said. "They were caught with the high water and a few of them swept away and one of them kind of hung onto the wall."

Witnesses said water somehow escaped from the 91-metre-tall Cleveland Dam, which holds back the man-made Capilano Lake upstream. Officials have not commented on what might have caused the dam to open.

"We're not able to say what caused this increase in waterflow at this time, but that will be part of the coroner's investigation and any additional or subsequent investigation that happens in this case," DeVries said.

In statements posted on social media, Metro Vancouver said the dam's spillway gate released "a large volume of water" during maintenance. The regional authority said the problem was resolved in the afternoon and that a full investigation had been launched.

Metro Vancouver commissioner Jerry Dobrovolny offered similar comments when speaking to media Thursday afternoon.

"Certainly it is a very serious matter," he said. "We are very concerned about what happened and it affected a great number of people and the investigation will leave no stone unturned."

Readings on the Metro Vancouver website give an indication of how rapidly the river surged on Thursday. They show the water level suddenly rising from about 0.6 metres up to 4.2 metres before dropping down again just as quickly.

The water flow simultaneously sped up, reaching 400 cubic metres per second before returning back to normal.