More than 140 Los Angeles firefighters have responded to a large fire that caused the roof to collapse at a commercial building in the San Pedro area.

City Fire spokesman Brian Humphrey says the blaze was reported around 4:15 a.m. Monday at the one-story structure.

Crews knocked down the flames in about two hours.

Humphrey says a fire captain was taken to a hospital for treatment of "exertion."

Surrounding streets have been shut down and at least two Metro bus lines are diverted.

The cause of the fire is under investigation. A damage estimate was not immediately available.