The cause of Wednesday night's fire at 325-333 Main St. is under investigation. (CBC)

Two dozen firefighters were called in to battle a fire in Saint John's north end Wednesday night that forced dozens of people from their homes.

Flames shot about 10 metres in the air, and thick, black smoke billowed from 325-333 Main St. as firefighters worked to knock down the blaze.

An estimated 45 people were forced from their homes and the street was blocked to traffic.

No one was injured.

Firefighters were called at about 6:30 p.m., said Deputy Fire Chief Mark Gillan.

By the time they arrived, flames were shooting from the rear of the complex structure, which includes Batch Bakery, about 15 apartments, some businesses and storage areas, he said.

"Right now, we are rooting out a deep-seated fire that is in between walls and in roof structures in the back of the building," Gillan said. "So we've got a substantial volume of fire and some very hard work ahead of us here."

Gillan said it's too early to speculate on the cause, but damage was contained to about 15 per cent of the structure.

Second fire at building

This was the second fire at the building in as many years and at least the third on that block.

"Those type of details certainly aren't lost on us," Gillan said.

In February 2007, six people were left homeless and a firefighter was sent to hospital after a tenant set fire to the curtains in his third-floor bedroom. That fire also forced the closure of Batch Bakery, which is located on the street level, for several days.

"It's quite disturbing," said Joan McInnis, who lives in a nearby building. "That's twice now in less than [three] years a major building — landmark building — burned. So it's kind of sad.

"We're trying to fix up the North End, and here they're tearing them down on us … through fire," she said.

"It's sad to see [the bakery owner] going through this a second time … I feel really bad for him — and myself because I'm going to miss my bread if he doesn't stay there."

Last April, 15 people were left homeless by a fire in an adjacent apartment building at 347-355 Main St. The building was 150 years old but newly renovated.

Red Cross officials were on the scene Wednesday to assist the displaced residents.