Fremont fire crews responded to a brush fire Sunday in the bay marshlands that spread to an old train trestle near the Dumbarton Bridge.
The fire was reported about 5:12 p.m., and burned about three-quarters of an acre near Dumbarton Point, said Battalion Chief Kyle Adams. The fire then spread to the trestle, and as of 7:30 p.m. Sunday, about 100 yards of the old wooden structure was burning, including a stretch west into San Francisco Bay, Adams said.
Both the trestle and the grasslands proved hard to reach, Adams said, taking firefighters almost 30 minutes to reach it. Firefighters needed to use four-wheel-drive rigs to reach the fire.
Authorities at the scene were unsure who has responsibility over the trestle.
The old rail bridge, which connects Newark and East Palo Alto-Menlo Park, hasn't seen trains for decades. But Facebook, whose main campus is near that rail line in Menlo Park, is negotiating with the San Mateo County Transit District to improve the Dumbarton corridor, including reviving the rail bridge, for operation by a commuter rail agency.
No further details were immediately available.