Five workers were injured, four of them seriously, when a third-floor balcony collapsed at a residential construction site in Gatineau Friday morning, paramedics say.

It happened at about 8:45 a.m. at 12 rue de l'Horizon in the Plateau area, where developer Brigil construction is building condominiums.

The collapse of the balcony caused masonry workers to fall about seven metres.

Rescue firefighters 12 rue de l'Horizon Gatineau construction site

Firefighters used a crane to lift an injured worker off the third floor of a residential construction site in Gatineau Friday morning. Five workers were injured when a balcony collapsed. (Radio-Canada)

One of the five workers on the balcony felt it begin to collapse and managed to jump onto the third floor of the unfinished condo building before the balcony fell. He suffered an ankle fracture and a back injury in the process, firefighters said.

There are no stairs to the unfinished floor, so Ottawa firefighters were asked to bring in a high angle rescue team to help get the injured worker off the third floor.

It took about an hour and a half to get the worker out. Firefighters used a crane to lift the worker off the third floor and into the care of paramedics waiting on the ground.

Brigil condo development 12 rue de l'Horizon Gatineau Aug. 18 2017

The construction site sits on rue de l'Horizon in the Plateau area. (Jérémie Bergeron/Radio-Canada)

'We're looking deeply into the situation'

Four of the five workers were taken to hospital in varying states of consciousness, paramedics said. Some of them suffered fractures. Their injuries are not considered life-threatening.

Quebec's occupational health and safety committee is investigating.

Denis Bouchard, a Brigil vice-president and spokesperson, said the workers are employees of a masonry company subcontracted by Brigil to carry out work at the site.

"We're looking deeply into the situation. The work will stop for a while [due to] the inquiry," Bouchard said.

View a map of the work site here.