Firefighters Saturday knocked down flames inside a two-story commercial building in Lincoln Heights, authorities said.

Firefighters dispatched at 12:08 p.m. Saturday to 647 S. Gibbons St., just east of the Los Angeles River, had the fire out within 31 minutes of their arrival, the Los Angeles Fire Department reported.

“One worker who had been inside the building at the time of the fire is being medically evaluated at scene by LAFD paramedics,” the LAFD’s Brian Humphrey said.

The structure is a generator service and parts warehouse.

The cause of the fire is under investigation.