SAN FRANCISCO -

San Francisco firefighters are battling a four-alarm fire burning in a building along the city's waterfront.

Fire Department spokeswoman Mindy Talmadge says more than 100 firefighters are trying to "surround the fire and drown it out." Talmadge says no injuries have been reported.

The blaze is burning in a mostly vacant building on Pier 29. It's not known what sparked the fire, which was reported at 1:50 p.m. Wednesday.

Large flames and thick black smoke are coming from the building. The pier is located on The Embarcadero, near Chestnut and Lombard streets.

Traffic has been stopped along the roadway, which is a main route along the city's waterfront. People are being advised to avoid the area.

San Francisco transit officials say the fire is disrupting transit service in the area.