Three people were killed and three others wounded when at least two gunmen opened fire as partygoers left a California warehouse.

The gunmen started shooting as a group of people walked out of the building around 1.20 a.m. yesterday, police Sgt Doug Calgano said.

Three people were pronounced dead at the scene. Police did not know the condition of the three wounded people. Roger Kiel told San Francisco television station ABC7 that his daughter, Shanice, 19, was one of the people shot dead.

At least 100 people attended the party at San Leandro, which had been advertised on the internet, Sgt Calgano said. He was not aware of a permit being issued for the party, which would have been required for a gathering of that size.

As the shooting began, many of the partygoers fled.

“Obviously it was a chaotic scene,” Sgt Calgano said.

The gunmen were armed with semi-automatic handguns, but police have not determined how many shots were fired. Investigators were trying to establish if the gunmen had attended the party, or arrived as people left the party.

It was not clear if the gunmen were in a vehicle or on foot when they opened fire.