An arsonist has sent a dozen people to the street, and they are now looking for a place to live after their Dartmouth apartment building was set on fire Thursday morning as they slept.

Emergency crews responded to the building in the 30 block of Lakefront Road around 3:45 a.m. after several callers reported seeing smoke.

Police say 12 tenants -- adults and children -- were evacuated from the building. A Halifax Transit bus was brought in to provide a temporary shelter for the tenants.

“There was a fire at the top, and I think by one of the doors, there was some sort of thing left in front of the door, and then that caught fire,” said tenant Menay Jolicoeur.

Hannah Moore lives on the top floor. She says the fire seemed to affect a unit on the second floor the most - where she helped a young mother and child escape.

“The smoke was just billowing out,” Moore said. “It was crazy. It started in one of the tenants down below so we took out the screen window and helped her and her kid out.”

No one was injured and the fire was extinguished by 4:30 a.m.

Officials with Halifax fire can't say right now what led them to believe that this fire was set deliberately because the case is now under criminal investigation.

Halifax fire does say it appears it started in the hallway, but Deputy Chief Roy Hollett says it’s too early to say for sure.

“Until our investigators have a look at it, we don't take anything for granted, and we'll work with our partners in police to look at the fire cause,” Hollett said.

Counting this case in the past year, there have been 50 fires in the city ruled as suspicious or deliberately set.

Out of those, Halifax police conducted 32 criminal investigations and laid charges in three cases.

Most, including one last May at a South End  condo building, remain unsolved.

As the investigation in Dartmouth continues, residents are being allowed back into their apartments to retrieve some personal belongings.

For his part Jolicoeur is staying with his parents over the long weekend - after a very anxious morning.

A representative with the company that owns the building says tenants will not be returning tonight. One tenant said she won't be back by tomorrow either.

Meanwhile, investigators with Halifax's Integrated Criminal Investigation Division are asking anyone with information about this incident to call police.

With files from CTV Atlantic’s Heidi Petracek.