Police are investigating after a major fire destroyed a Longueuil apartment complex on Friday morning.

Firefighters responded to a call around 6:30 a.m for a fire that had started at an 18-unit complex and then spread to three neighbouring buildings.

Shortly after 8 a.m, officials were able to bring the fire under control.

Fire officials said they found traces of accelerants in the kitchen of the unit where the fire started.

Police now consider the fire suspicious.

Families left homeless

With their homes destroyed, many of the residents will have to stay with friends or family until they can find new lodgings.

Since police declared the fire suspicious, residents were not permitted to go back inside for any belongings that might have survived the flames.

Many of the residents had run outside in the early morning hours wearing nothing but their pajamas.

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Several apartments were destroyed in a major fire on Friday morning. (CBC)

One man said he had just moved into his unit on Thursday night and had yet to unpack a single box.

The Red Cross says it will help 20 of the families who were forced out of their homes on Dumont Street.

The organization will provide the families with the basic essentials for three days: shelter, clothing and food.

"We arrive with blankets, we arrive with teddy bears for the kids. It’s an important aspect," said Red Cross volunteer Ylrick Normandeau.

Police said no one suffered critical injuries in the fire, but three people including two firefighters were taken to the hospital with minor injuries.

All of the residents' pets managed to escape harm.