Firefighters remained on scene throughout the night into Tuesday morning as a fire that gutted a vacant century-old building in downtown Victoria continued to smoulder.

The former Plaza Hotel on Government Street went up in flames early Monday morning, shooting a tower of thick black smoke into the sky.

An investigation into why it sparked is ongoing.

A caretaker, Mike Draeger, remained unaccounted for in the aftermath of the fire.

Police are asking anyone who has seen him to contact them immediately.

"Our minds would be very much at ease if we determined he was somewhere other than in the building," Victoria Fire Chief Paul Bruce told reporters Tuesday.

Crews were unable to access some parts of the structure due to safety concerns.

“Fire continues to burn in places firefighters cannot safely access," Bruce said. "Some wood structures are at risk of failing."

On Monday, Bruce said it was too soon to say whether the blaze was considered suspicious, but signs point to it having been helped along somehow.

"There's significant fire damage, there's large wooden structures there, which indicates a long burning period," he said. "This is going to take us a while to sort all the details out."

Fire inspection officers were supposed to discuss a sprinkler system with the owners of the hotel Wednesday, Bruce said.

"We've had difficulty of being able to align our inspection times with somebody being on scene," he said. "When we did finally get in there, to the best of my knowledge...the arrangements were made that the sprinkler system wasn't up to code and they wanted that repaired quickly."

Bruce said he was "hopeful" crews would get the fire fully extinguished Tuesday, allowing them to proceed with an investigation into the cause. 

The fire choked downtown Victoria in thick, acrid smoke and lowered air quality, which shut down City Hall for a second straight day.

Bruce advised people to stay away from the scene because the smoke is "toxic."

"If you don't have to breathe it in, I don't know why you would," he said. "Some people seem to want to go down there and see the smoke."

Parts of Pandora Avenue, Government Street and Broad Street remained closed to traffic Tuesday morning as crews continued to work on the structure.