San Francisco firefighters were battling a three-alarm blaze Wednesday at a downtown waterfront pier that’s slated to host events for the America’s Cup yacht race. So far, no injuries have been reported. About 75 firefighters were fighting the blaze at the Pier 29 warehouse building, San Francisco Fire Department Capt. Jeanne Seyler told CNN. The cause of the blaze, about a mile from the popular tourist site of Fisherman’s Wharf, was not immediately known, Seyler said.