The fire started just after 5 a.m. Friday inside the ground-floor restaurant. It was extinguished about an hour and a half later by 40 firefighters.
Fire department operations chief Ian Ritchie said the fire could have been intentionally set.
"There are certain indications that we have in the fire scene that it was suspicious, therefore the fire will be transferred to the Montreal police department," Ritchie said.
He said the fire did not spread to the second floor of the two-storey building, but that it and the neighbouring buildings on either side were evacuated as a precaution.
He said the 20 or so people who were forced from the buildings will be able to return to their homes at some point this morning.
The water used to put out the fire has left the road slippery. Parc Avenue will remain closed in both directions between St-Viateur and Fairmont avenues until public works can salt the street.