Roofing work caused a four-alarm fire at the Lockheed Martin Plant in Oldsmar on Tuesday afternoon.
Crews were applying hot materials to the roof of the facility at 3655 Tampa Road, and a fire started about 1:40 p.m. The fire sent black smoke billowing into the sky and forced the evacuation of about 500 employees.
Firefighters from several Pinellas County stations raced to the scene and put out the fire in about an hour.
The response was upgraded to a hazardous materials call as a precaution.
"With hazardous materials, it's a slow and steady process," Oldsmar Fire Chief Dean O'Nale said. "They don't want to rush into something they don't know about so initially they'll recon the area and start doing some sampling. If there's a problem that needs to be taken care of like a leak, they'll do that."
No injuries were reported. The employees were allowed back into the building after about an hour.
"There was an incident at our Clearwater (Oldsmar) facility," Lockheed Martin spokesman Keith Little said. "We immediately evacuated the building, and all employees have been accounted for."
Pinellas County Fire Rescue dispatchers confirmed that first responders saw smoke and flames from atop the building.
Lockheed Martin, which specializes in aeronautics systems, has two plants in Pinellas County. The Oldsmar plant manufactures and assembles military and commercial products. There are no chemicals located near the fire, Little said.
Officials said that so far there doesn't appear to be any damage to the actual facility, and that all damage was contained to the roof.