Investigators look for clues to the fire Wednesday morning. (CBC)

Dartmouth police are investigating a suspicous apartment fire that forced dozens of tenants to flee early Wednesday.

Thirty people fled 88 Queen Street at about 12:45 a.m. as the blaze ripped through the three-storey brick building.

One apartment was gutted and other units suffered extensive smoke and water damage, The Canadian Red Cross said.

Halifax Regional Police said no one was hurt.

Fire crews called police when they began to suspect the fire had been deliberately set, Const. Brian Palmeter said.

"That scene has since been turned over to police as it's been determined that the fire is suspicious in nature," he said. "Fire investigators will look into the cause of the fire and then our investigators will look at the criminal aspect."

Police have been called to the building before, but Palmeter said nothing suggested the fire was related to previous incidents.

Police and fire officials spent the day combing through a first-floor apartment, where suffered much of the damage.

Palmeter said police were speaking with neighbours and asked witnesses to come forward.

The Red Cross said 18 tenants have been allowed to return to their apartments, but six others would have to seek other accommodations for now.