CONCORD -- The mezzanine on a suite that housed a roofing company business caught fire Thursday morning, but nobody was injured and neighboring businesses were unscathed, authorities said.

The one-alarm fire started at 9:37 a.m. inside a building located at 970 Detroit Ave. and was preceded by a popping that sounded like a "mini-explosion," Battalion Chief Dominic Ciotola of the Contra Costa Fire Protection District said. The building's owner heard the popping, and immediately left the building, Ciotola said. Nobody else was inside, he said.

Fire officials said it was no immediately known where the small explosion came from, but Battalion Chief Andy Steffen said that "everything at this time is pointing to an accident."

The company, Crest Roofing, Inc., is located in a suite inside the building, and the mezzanine is where the fire was knocked down, Ciotola said. Crews from four engine companies and two fire trucks needed 20 minutes to extinguish the blaze, he said.

A cashier for Salsa Verde, a Mexican restaurant located next door, said smoke sometimes comes from the chimneys at the building, so initially she didn't realize the smoke she saw Wednesday was indiciative of a blaze.

"People just started screaming trying to make sure nobody was inside," Monica Velasco said. "Someone came running out. It was scary."

Much of the damage done to the building came from the smoke, Steffen said. It was estimated that the monetary damages would equal $100,000, he said.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.