Fire that destroyed part of the Regina Shake Shop early Sunday morning was deliberately set, fire officials said Monday. (Regina Fire Department)

A massive fire that ripped through a Regina lumber supplier on Sunday was deliberately set, the city fire department says.

The blaze that was reported shortly after 2 a.m. MT at the Shake Shop in the city's warehouse area caused about $500,000, the fire department said.

Fire officials said Monday that the fire started in a vehicle parked on the south side of the building before spreading to the interior of the building. Investigators have since determined it was deliberately set.

Firefighters spent hours pouring water on the blaze, but by the time it was under control later Sunday morning, half the building was gone.

Investigators believe the fire started in one of the cars parked alongside the building. (Sheryl Rennie/CBC)

Sunday afternoon, a row of burned out vehicles could be seen along the building, and behind them was a gaping hole where the warehouse walls used to be.

Wet, black chunks hung down from the remnants of the roof and charred heaps of equipment could be seen inside.

But if it looked like a mess, fire department spokeswoman Angela Prawzick said it could have been worse.

The cedar lumber that was piled along the back of the building and the north wall was dripping wet, but intact.

"Crews were able to contain it before it got to the cedar, so we're looking at a building that's significantly damaged, but not a building that's destroyed," Prawzick said.

Business manager Dan Crosby was hopeful he and the four other employees would be able to reopen.

"I just walked inside. It's not as bad as it looks. We can probably still keep going," Crosby said.

Crosby said he'll have to talk to the owner, and they'll decide what to do next.

The investigation into the fire has been turned over to the Regina police, fire officials said.