A 27-year-old runner in Toronto's waterfront marathon has died.

Bruce Minnes, medical director of the marathon, said Sunday afternoon that the man had no vital signs when he was taken from the course about 300 metres from the finish line, at around 11:15 a.m. ET.

Toronto Emergency Medical Services said the man was transported to St. Michael's Hospital from Bay Street and Wellington Street West.

Police from Toronto's 52 Division said he died at St. Michael's and confirmed he was a participant in one of the races that were part of the event — the marathon, half marathon and five-kilometre runs.

It's not immediately clear what caused his death.

"The individual received an immediate response from a bystander who initiated CPR with Scotiabank Toronto Waterfront Marathon’s first response units, two EMS crews and 911 response attending within moments," Minnes said in a release.

The marathon organizers are not releasing any further information until "all the proper notification procedures have been followed," Minnes said.

Around 22,000 people are participating in the runs, which are taking place on a large stretch of the city's waterfront.