Three people were killed in a small plane crash Thursday in a lagoon in the US state of California, authorities said.

The plane, a twin-engine Beech 65 Queen Air, crashed in the Redwood Shores area at around 11:51 a.m. local time, just 30 seconds after taking off from San Carlos Airport, about 30 km south of San Francisco, Xinhua reported.

The body of a woman in her 40s was first pulled out of the water and rescuers believed more people may have been aboard the plane. Several hours later, two male bodies were found among the wreckage in the water.

One of the male victims was confirmed to be 91-year-old Robert Borrmann, founder and president of R.E. Borrmann's Steel Co. Local authorities said the other two victims were Borrmann's pilot and the pilot's girlfriend.

'It was quiet and then all of a sudden it sounded like a dive bomb followed by a deep thud,' Josh Butler, who saw the crash from his office, told Xinhua.

'When we looked up we saw it upside down in the water and as it sunk, pieces from inside the cockpit were floating around outside in a big oil slick,' Butler said.