After three hours of work in miserable weather conditions, firefighters have been able to control a blaze at a commercial building in Toronto’s Chinatown neighbourhood.

The fire broke out on the second floor of a building on Spadina Avenue, near Dundas Street, shortly before 10 a.m.

Due to the proximity of the fire to a number of adjoining buildings, Toronto Fire Chief Matthew Pegg said crews ramped up their efforts almost immediately. At least 17 trucks and 65 firefighters were reported at the scene.

The fire quickly escalated to a third alarm.

Crews then transitioned into a “defensive attack,” Pegg said, and withdrew from the inside of the building due to concerns about the safety of the floor.

Firefighters inside the building reportedly encountered extremely high heat and low visibility due to thick smoke.

“Unlike what we see portrayed on TV, being in a real fire is completely black. It’s not bright. It’s black, it’s blinding and it’s thick. Our crews were working in those conditions,” Pegg said.

“There came a point in time when the officers inside the building were encountering excessive amounts of heat and then began having concerns about the structural integrity of the floor.”

Initially, it was reported that one firefighter was taken to hospital for "observation,” but was later determined to be OK.

There are no other injuries.

The fire was deemed under control by about 1 p.m., however crews remained on scene dealing with possible hotspots and ensuring that there is no extension to adjacent buildings.

Due to the size and “estimated loss” caused by the fire, the Ontario Fire Marshal has been notified and will visit the scene.

“I have no indication yet as to where the fire started or what the origin, cause or circumstance is,” Pegg said. “Once the investigation gets underway, once it’s safe for our investigators to get inside, we’ll be able to begin that process, but I won’t know for some time”

The inclement weather conditions made it challenging for crews to tackle the large fire. Pegg said the freezing rain coated some equipment in ice and made it tricky for firefighters to access certain areas of the building.

“It’s slippery. There is a lot of snow and ice pellets on the ground. It’s raining, people are wet. Being wet, having wet firefighting gear is problematic,” Pegg said.

“It just makes everything a little bit slower and a little bit harder, but as always, they did a great job.”

Roads in the area were closed but have since reopened.

The closure was blocking some TTC streetcar routes in the area. The TTC was required to disconnect power to some of the overhead lines powering streetcars in the area so firefighters could safely operate tower ladders.

However, Pegg said he hopes to scale back the number of crews and open at least one lane of traffic in the near future.

“Our our goal certainly will be to have all four directions of this intersection open in advance of rush hour,” he said. “We will do our very, very best to make way for the TTC, as well.”