Saint John firefighters continued to battle a blaze at the ServiceMaster warehouse on Westfield Road, on the city's west side, into the evening on Thursday.

The building, located at 860 Westfield Rd., is a write-off, but crews were still trying to extinguish small patches of flames and hotspots as smoke continued to billow from the scene.

Fire Chief Kevin Clifford told CBC News it was difficult to speculate how long it would take.

There is no word yet on the cause. No one was injured.

Meanwhile, the City of Saint John was advising motorists that Bay Street was closed from Gault Road to the Bay Street bridge. Some people were trying to drive around the barricades, according to one RCMP officer at the scene.

Motorists were being asked to use alternate routes and not to drive over the water lines being used to fight the fire, officials said.

A few NB Southern Railway trains were also delayed because the main hydrant fire crews were relying on is across the tracks.

Used to store flood, fire victims' belongings

The ServiceMaster warehouse in Saint John, which stored the belongings of flood and fire victims dealing with insurance claims, was destroyed by fire on Thursday. (Jessica Doria-Brown/CBC)

Crews were called to the scene over the lunch hour to find the building fully engulfed and to be faced with several challenges, said the chief.

They were concerned about several propane containers in the area, Clifford said.

"Soon as we're comfortable around the tanks and as soon as we're comfortable that we've cooled down the area where the propane cylinders are, then we can try to demobilize, but right now we're still fighting an active fire that presents some hazard to the community," he said.

In addition, fire crews were unsure exactly what inventory the warehouse contained, so they were concerned about what was in the smoke and what was in the runoff water with the bay nearby, Clifford said.

Department of Environment officials were called in.

City crews helped to divert the runoff from getting into the waterway with booms and by building a dike system with gravel. They also covered a few drains.

"Better safe than sorry," said Platoon Chief Peter Saab.

Fire crews were out of the range of danger in terms of smoke inhalation because it was an outside fire and they ended up using a defensive approach, he said.

'Gave it their all'

Thick black smoke could be seen from Saint John all the way to Grand Bay. (Rachel Cave/CBC)

About two dozen firefighters "gave it their all," trying to snuff out the fire for the first half hour, but quickly realized they had to change their approach, said Saab .

"Tried to do an aggressive interior attack when they first arrived, but ran into such heavy heat and fire that we pulled crews back out to try to vent the building," he said.

"We then re-entered the building hoping to get a handle on the fire front, but once again we ran into so much fire and heat — and the integrity of the building, because of the amount of fire that's been burning, we were worried it was compromised, so we pulled crews at that time and decided to make it a defensive action."

The size of the building and metal exterior made it difficult to get out all of the hot spots, said Saab.

"We've switched over to some foam action, that's going to help us out a lot."

Everyone safe

Chris Long, who owns the ServiceMaster warehouse, said he is relieved everyone is safe.

"Everything will be totally destroyed. The number one thing is that all of our employees are safe. We actually had a couple of our insurers over here, and they also got out and are safe. So really, that's the most important thing right now," he said.

"The next thing is to start the triage information to our insurance partners and we've started that process already."

Long said he feels badly for the people who were storing their belongings in the warehouse. They are flood and fire victims who are dealing with insurance claims, he said.

One couple was about to pick up a grand piano, Long said.

A large teak boat was also among the items destroyed, he said.