A quarter of the pier at Fisherman’s Wharf “has been lost to the flames,” according to Lt. Jonathan Baxter, a public information officer with the San Francisco Fire Department. The warehouse was destroyed.
One firefighter had a severe cut to his hand and was being treated at a local hospital, Baxter says. He is expected to recover. No other injuries were reported.
The pier was fully evacuated, as were some nearby businesses, the fire department says.
Flames could be seen in the early morning darkness in photos tweeted by Dan Whaley.
The blaze was first reported at 4:17 a.m. local time (7:17 a.m. ET) and was contained to a section of the pier.
The Fire Department tweeted a link to live updates.
The fire caused a partial building collapse on the southern part of the pier, spread to two buildings on the pier and is in danger of spreading to a third, fire officials say.

“When firefighters arrived, the flames were literally lapping over the Jeremiah O’Brien,” he said, CNN affiliate KPIX reported. “They literally saved the O’Brien.”
Reporter Reyna Harvey of affiliate KRON tweeted video from the scene.
Several fireboats are positioned around the wharf and helping fight the fire.
The warehouse contained a large fish processing operation for the northern California crab fleet, KPIX reports.
The fire department is working with the city’s Department of Building Inspection and the San Francisco Port Authority to determine the structural integrity of the pier.
It remains unclear whether anyone was in the building, which is sometimes used by homeless people, officials said.
Investigators are scrubbing through surveillance footage to determine the cause of the fire.