The death of the 14-year-old boy was the second death at the Mont Saint-Sauveur park in as many weeks. (CBC)

Police have confirmed that a 14-year-old boy who died at a water park north of Montreal on Monday had a heart condition.

The death was the second in two weeks at the Mont Saint-Sauveur water park in the Laurentian region.

The boy was walking up the stairs toward one of the waterslides when he lost consciousness and fell, police said.

The incident occurred at about 11:30 a.m. near the slide known as the Colorado River, police said. The boy's death was confirmed about an hour later at a nearby hospital.

"One of the major hypotheses we are working on was it was probably heart failure," Sgt. Benoît Richard said.

"People in the stairs and, of course, people from Mont Saint-Sauveur, did CPR until the ambulance arrived."

An autopsy will be performed to determine the cause of death and whether it could be related to the extreme heat, Richard said.

There was a high heat and humidity warning in effect for the region as temperatures rose to the mid-30s.

Mont Saint-Sauveur spokesman Christian Dufour said the park will follow up on any safety recommendations.

"For now, this seems to be an isolated case where a young person … simply had heart problems," he said. "For other incidents, of course, security is the main priority for our organization so we're following up with the Régie du bâtiment du Québec [the province's building inspection board] and the [police]."

A nine-year old boy drowned June 23 in the wave pool at the park. A coroner's investigation has been opened into that incident, which park officials said was the first death at the facility in its 24-year history.