Investigators are trying to determine how a house under construction in Mirabel partly collapsed Monday night, killing one man.

The accident happened on a property on Jade St. near Cristal St. in a house that was in the early stages of construction.

“they were on the roof and they were trying to unload a shipment of wood from the crane,” explained Cindy L’Heureux of the CSST, the province’s workplace safety board. “That's when everything came crashing down and we're still trying to figure out why.”

Crews had already erected the frame of the house and installed vapour barriers on several sides, and were accepting a delivery of boards for an upper floor when part of the building collapsed.

Two men fell 3 metres to the ground. One man died almost instantly, while a second was seriously hurt and taken to hospital.

Andre Belanger, who works for local roofing company Structure du Nord, said the structure may not have been secured properly. Weather could also have been a factor, he said.

“For about two or three days we have a lot of wind, so when you have enough wind like that, you have to be careful, thinking, and watch out when you (secure) that top,” he said.

There are unconfirmed reports the owner of the home was the one who died, but police will not reveal his identity until his family has been notified.

Mirabel police would only confirm that the body of a construction worker in his 40s was removed from under the debris, and that the victim lived in the area.

Neighbour Stephane Morin said he met the homeowner several times over the past year.

"I know the owner a little bit, I was passing by all summer long and he was cutting the trees on the lawn," said Morin.

The CSST is investigating the incident and will try to determine what led to the collapse and death.