At least seven people have lost their lives and one seriously injured in two related incidents in the US state of California on Monday making the second carnage in the country during the past 48 hours.

The latest carnage in the western US state came less than 48 hours after a gunman shot dead 11 people at a Lunar New Year celebration near Los Angeles on Saturday night.

San Mateo County Board of Supervisors President Dave Pine said four people were killed at a mushroom farm and three at the trucking business on the outskirts of Half Moon Bay, a city about 48km south of San Francisco.

Pine said the suspect worked for one of the businesses, calling him a “disgruntled worker”.

Sheriff Christina Corpus, speaking at a news conference, said the 67-year-old was taken into custody after driving to a sheriff's substation in Half Moon Bay where he was pulled to the ground by armed officers.

"Shortly thereafter three additional victims were also located deceased with gunshot wounds at a separate shooting scene," she told reporters.

California has witnessed two mass shootings in the last week, with the police saying that suspects in both cases used semiautomatic handguns and both appeared to have connections to at least some of the victims.

California Governor Gavin Newsom called Monday's shootings another “tragedy.”

"At the hospital meeting with victims of a mass shooting when I get pulled away to be briefed about another shooting. This time in Half Moon Bay. Tragedy upon tragedy," he tweeted.