Suffolk firefighters spent nearly three hours Tuesday battling a blaze that destroyed a modular office at the Virginia Department of Transportation headquarters.

The 12 units responding to the fire in the 1700 block of North Main Street around 9:45 a.m. found the single-story building engulfed in flames and smoke, said Capt. Jim Judkins, spokesman for the Suffolk Fire Department. The building had been evacuated before firefighters arrived.

The fire, which appeared to have started in the roof line around the building’s heating system, had begun to spread to a second modular unit when firefighters arrived, Judkins said.

Witnesses later reported seeing flames on the building’s exterior near the heating unit.

The blaze caused $54,000 in damage to the building and its contents.