SAN DIEGO -- A fire burned a wooden railroad trestle Saturday night, disrupting train service. The blaze was reported about 9:15 p.m. and burned the trestle and surrounding grass near Interstate 5, according to the city Fire Department.

According to a wire service, no homes were threatened and the freeway remained open as more than 30 firefighters battled the fire, which was contained in about 1 1/2 hours.

One firefighter suffered a back injury but it was not life-threatening, a fire spokeswoman said.

The blaze partially collapsed the trestle, disrupting tracks used by freight trains and the Metrolink and Amtrak passenger lines.

Amtrak officials said at least one train from San Diego to Los Angeles was unable to proceed Saturday night, and it could take two days for service to resume. About a dozen Amtrak trains cross the trestle daily, officials said.

Train passengers will be taken by bus to their train stops.

The cause of the fire was under investigation.