The cause of an early Friday fire that destroyed a former Athens upholstery shop is under investigation, an official said.

Athens Fire & Rescue Service Chief Bryan Thornton said firefighters received a call about 2:30 a.m. for a smoke investigation on Chestnut Street. While en route, dispatchers alerted firefighters to an active blaze at the intersection of North Clinton and Walnut streets.

When they arrived on scene, Thornton said the entire building was on fire and about 75 percent of the roof was burned through.

“All we could really do — because the block walls were leaning — we had to go full exterior defensive mode and fight it that way,” he said. “(That means) nobody goes inside inside the structure and all hose lines are directed from the outside.”

It took firefighters nearly an hour to get the flames extinguished. Firefighters and employees from Athens Public Works were back on scene Friday morning.

Before crews were able to get inside the building to investigate, Thornton said they had to first secure the area and make it safe to enter.

There are no reports that indicate anyone was in the building at the time of the fire and Thornton said there was no power going to the building.

“We really don’t know at this time what we’re dealing with,” he said. “We just know there was a fire and none of the firefighters were injured.”