Crews are battling a four-alarm fire burning at a warehouse at Pier 45 at Fisherman's Wharf Saturday morning.
The fire started around 4:40am and as of 5:49 a.m., the fire department said crews were making progress on the flames.
Additional structures and the SS Jeremiah O'Brien ship (one of two remaining fully functioning Liberty ships launched during World War II) were threatened by the fire.
The warehouse is a total loss.
It's unclear what ignited the flames and investigators are now working to learn the cause and origin of the fire.
A total of 145 firefighters responded to the scene and fire crews are expected to be at the pier through the afternoon.