A day after a massive, six-alarm fire gutted a foam factory in north Toronto, there are questions about whether or not the building had a functioning sprinkler system.

Fire crews battled the blaze throughout the day Thursday. The fire sent massive smoke plumes into the sky that could be seen across the city.

Fire officials who spoke to CBC News Thursday said they do not yet know whether or not the factory, which makes foam for beds and other products, had a working sprinkler system but did say the blaze spread very quickly.

"Often sprinklers do contain a fire, in this case the fire did get out of control and consumed the whole building," fire captain Mike Stampko told CBC News.

John Galt is president of the Canadian Automatic Sprinkler Association. He says companies like FoamCo are required to have special robust sprinkler systems. Because of the speed and size of this fire, he wonders if the sprinklers in the building were up to code.

"A properly designed system would be putting a larger volume of water on a given fire in an average scenario and it would control the fire for the fire department to respond," he said.

The company declined comment. Fire officials say the building will most likely have to be completely torn down and that determining a cause could take weeks. Damage is estimated in the millions of dollars.

Toronto Fire Services responded just after 8:30 a.m. to the fire at 198 Fairbank Ave., near Castlefield Avenue. That  location is just north of Dufferin Street and Eglinton Avenue. The fire was originally listed as a two-alarm fire and was upgraded to six alarms shortly after 11:30 a.m.

Toronto Fire Services Deputy Chief Mike McCoy said firefighters confirmed that no one was inside the building, and quickly began fighting the fire from a defensive position.

"We're settling in for what's going to be a long afternoon," said McCoy on Thursday. "The fire is moving around inside. As we get a handle on it on one way … it runs to the other side of the building."

There were concerns about chemicals present in the smoke from the fire. The building is full of stacks of mattresses made of foam, rubber and other materials.

Because of the direction of the wind, many people near the building complex did not have to leave their homes.

"We're got a breezy day, [the smoke is] dissipating fairly rapidly," said McCoy. "It wasn't heavy enough that it's causing us concern."

Students kept inside school 

Toronto Fire Services issued a message on Twitter, calling for people to stay inside and keep windows closed if smoke is in the area — especially north of the fire.

Students at more than 10 nearby schools were kept inside, with some schools shutting down ventilation fans and others sending students home early.

“First we smelled burning inside our classrooms so we closed up the windows, then we were aware there was a fire,” said student Shania Walker.

Staff from Ontario’s Ministry of the Environment were on the scene monitoring air quality.

“The good news is the readings have been low, they're talking with their hazardous materials technician right now,” said Mike Strapko with Toronto Fire Service.

A total of 30 trucks and more than 120 firefighters responded, including multiple aerial units. Some nearby buildings were also evacuated.

During the fire police closed Dufferin Street between Wingold and Castlefield Avenues.

With files from CBC's Steven Bull, Lorenda Reddekopp