A fire inside an air filter housing for the gas turbines at the GWF Energy Tracy Peaker Plant on Tuesday might have been caused by a welding crew working to turn the facility into a full-time power plant, according to officials.

GWF Director of Engineering Hal Moore said he was notified about the fire inside the West Schulte Road power plant at 2:40 p.m. He said a welding crew of fewer than 10 employees was working on the plant conversion inside the building, and officials think the workers might have ignited paper air filters there.

Moore said all employees in the area of the fire were evacuated, and no injuries were reported.

Tracy Fire Department officials reportedly got the call at 2:44 p.m., sending more than five engines to the plant. A ladder truck from the Sharpe Depot fire department in Lathrop also responded to the call, because the Tracy ladder truck is undergoing repairs.

A plume of black smoke rising from the plant could be seen for several miles as it drifted into the sky.

At the plant, firefighters worked to extinguish the blaze and reportedly found that the fire hydrants there did not work.

Moore said the plant’s fire-protection system was ready but not operational, because the plant is not online. He noted that several water tanks store a total of 650,000 gallons of water.

Division Chief Dave Bramell said fire officials had been notified a few weeks earlier that the hydrants were not yet functional, because the plant is still under construction. He said it was a challenge at first to access the available water source — a nearby tank holding more than 100,000 gallons of water — to extinguish the blaze.

Bramell said about 20 firefighters battled the fire, which was controlled shortly after 4 p.m.

The facility — a peaker plant that has undergone upgrades since February to make it a full-time power plant — is designed to produce enough electricity for 325,000 homes once it is operational. The power it generates will be bought by Pacific Gas & Electric Co. under a 10-year purchasing agreement.

Michael Storm, director of projects for Wood Group GTS, said the welding crew that was working at the plant when the fire started was part of the ongoing construction to get the plant completed on schedule.

He said officials would not know the extent of the damage until crews can get inside the air filter building, but he said they hoped the fire would not prevent the power plant from going online in August, as expected.