A fire broke out before dawn on San Francisco’s Fisherman’s Wharf and destroyed a warehouse. Fire officials said one firefighter suffered a hand injury. Investigators were trying to determine whether homeless people were inside. The fire tore through the warehouse before dawn Saturday, sending thick smoke over the waterfront and causing its walls to collapse. At one point, it threatened to spread to a historic World War II-era ship that docks by Pier 45. But officials said firefighters successfully saved the vessel. The cause of the fire is under investigation.