Gainesville firefighters are trying to determine the cause of a Sunday night fire that gutted a 12,000-square-foot warehouse used by Mar-Jac Poultry.

Firefighters responded at 11 p.m. to the fire at the building off Airport Street near West Ridge Drive.

“Upon arrival, fire crews found heavy smoke and flames,” Fire Chief Jon Canada said.

The roof began to collapse early on, preventing firefighters from battling flames inside the building. From the outside, they worked to put out the fire and keep it from spreading, an effort that took at least 2 1/2 hours.

“The building had a heavy fire load in it,” Canada said. “It had a lot of paper products and plastic materials. There was some other machinery and things stored in there that were fueling the fire.”

Pete Martin, Mar-Jac’s vice president of poultry operations, said used equipment was stored in the building.

No firefighters were injured in the fire, even though they had to contend with frigid temperatures in their work.

“You get ice on everything in those conditions,” Canada said.

The fire department had to wait until daylight to “check the stability of the building a little bit more since we did have a (roof) collapse,” Canada said early Monday.

Firefighters also weren’t able to search the building immediately.

“To the best of our knowledge and (according) to the representative we’ve talked to from Mar-Jac, there shouldn’t have been anyone in the building,” Canada said.

“There had been reports to us of some use in that building from time to time of maybe some people breaking into (it) and using it for a shelter.”

Investigators spent Thursday combing through the building, or as much of it as they could access.

“There is one area where the collapse is completely down and a lot of stuff under it is still smoldering,” Canada said later on Monday.

No dollar amount on damage has been set.

“We’ll probably just get (the remaining structure) cleaned up and leave it like that,” Martin said. “We will not build it back, by no means.”