Public health officials are investigating a possible case of food poisoning that left more than 50 attendees at an NAACP gala with terrible vomiting and diarrhea.

Twelve people were taken by ambulance to hospitals and treated for dehydration, officials said. And several more drove themselves to hospitals Saturday night and early Sunday morning after getting sick during a banquet dinner commemorating the closing of the 27th Annual NAACP State Convention.

Among those hospitalized was former Oakland Mayor and Assemblyman Elihu Harris, said George Holland, an attorney who heads the civil rights organization’s Oakland chapter.

More than 300 people, including former San Francisco Mayor and keynote speaker Willie Brown, attended the banquet at the grand ballroom of the Sofitel San Francisco Bay Hotel in Redwood City, Holland said. He didn’t know if Brown had fallen ill.

Several people became sick after eating a dinner that included salmon and salad, Holland said. By 10:30 p.m. attendees were throwing up in the hotel lobby, while more than 20 firefighters and paramedics tended to them.

“It was a terrible scene,” Holland said. “Other hotel guests were very upset.”

Quite a few of the sick were teenagers attending the banquet, Holland said. A 5-year-old also fell ill.

Holland said his wife started vomiting early Sunday, and the illness hit him Monday morning. “I was shivering all day long,” he said.

Sofitel, which is part of a French luxury hotel chain, did not return a call seeking comment. Health officials were unable to produce records Tuesday showing whether the hotel has had similar issues in the past, said Robyn Thaw, spokeswoman for the San Mateo Medical Center.