Investigating the cause of a fire at a hotel under construction in Saskatoon will be difficult, if not impossible, because of concerns about the building’s structure, according to the city’s fire department.

Assistant Chief Wayne Rodger told media early Wednesday afternoon — about eight hours after the fire broke out at the building on Lorne Avenue — fire crews are not able to enter the building because of stability concerns.

“We fear there is a potential for collapse,” Rodger said. “We don’t want to subject our staff to those kinds of conditions.”

Determining the cause of the flames may not be possible.

“If there’s no way to secure the stability of that building, we may not be able to,” he said when asked how fire crews will investigate the blaze.

The fire started at about 6:30 a.m. Wednesday in the upper floors of a tower of the building, according to Rodger.

Two explosions caused by propane tanks on the site could be heard shortly after firefighters arrived, and, by 8 a.m., smoke was seen billowing into the sky from the building.

Flames were under control — meaning the fire was no longer growing, according to Rodger — by about 9:15 a.m., but some hot spots remained as of 2 p.m.

Rodger said the fire department, which began leaving the site at about 2 p.m., would be on call in the event the fire flares up.

“We’re working with the contractor and site manager to provide a fire watch, and if something should start up here, they’ll get in touch with us, and we’ll be a presence here once again,” Rodger said.

Security will be monitoring the site, according to the fire deparment.

A number of traffic restrictions were in place in the area for several hours, as emergency crews responded.

No injuries have been reported, and Rodger said the fire department was told no one was inside the building at the time of the fire.

He was unable to provide a damage estimate, noting determining the cost of damages for fires on construction sites is difficult.