04/24/2015 09:18 EDT | Updated 07/22/2015 07:59 EDT

STM bus fire cause still unknown

The public transit bus filled with commuters that caught fire had been subject to a recall last summer because of an alternator problem, but the STM says the part in question was replaced in January.

There is still no definitive cause of the blaze that enveloped the Nova bus shortly before 3 p.m. yesterday in the eastbound lanes of Highway 720.

"It's too early to make any connection between the incident of yesterday and the recall of last summer," STM spokeswoman, Amélie Régis, told Daybreak.  

"We must proceed with the investigation first to know the cause of the problem."

The bus, a 2010 model, was completely destroyed in the fire.

One woman who was on the bus said passengers had to climb out a window because the driver had pulled over on the right side of the highway, which was up against the railing.

Quebec provincial police confirmed that all passengers got out safely from the 485 bus that was headed toward Lionel-Groulx Metro station when it caught fire.

A passenger said she heard what sounded like a small explosion before the fire broke out.

Régis said a technical investigation is now underway to pinpoint the cause of the fire. An inspector from the bus manufacturer is assisting with that investigation.

She said the STM has maintenance plans for all its buses that includes a mandatory inspection every six months or 20,000 kilometres.

Brakes and tires are also swapped out every 10,000 kilometres.

"The investigation will tell us what the problem is, but when we heard about the recall last summer, we conducted a sample audit of the buses involved and we found no particular problems," she said.

"The bus were still safe. You have to know that we take safety very seriously."