UPDATED 6:30 p.m. BLOOMINGTON - A fire early Saturday that caused extensive damage to a building on West Front Street in downtown Bloomington started in a stairwell up to the third floor, fire officials said.

Firefighters were called out just after 2:15 a.m. in near zero-degree temperatures after report of a fire in the 100 block of West Front Street, said Assistant Fire Chief Gary Sushka. Crews had knocked the fire down in about 15 minutes, he said, and only sparse smoke was visible from the street before 3 a.m.

The building has four apartment units on the two floors above the Canteen bar, 107 W. Front St., fire officials said. A unit on the third floor where the blaze appeared to be concentrated had extensive fire and smoke damage, with other units having some smoke and water damage, officials said.

There were no injuries reported, Sushka said, but it was unclear later Saturday how many of the units were occupied at the time of the fire or if anyone was home.

Assistant Fire Chief Nick Issacs said the cause of the fire has yet to be determined, but it started in the stairway. The investigation into the fire continues, and a dollar amount on damages will be determined.

No damage was apparent to the street side of the building Saturday night, but the Canteen remained closed.

Four fire engines, two trucks, and one mutual aid unit from Normal were called up to fight the blaze.