According to a source close to the investigation, two passengers suffered minor burns. The third person was injured badly.
The plane's pilot told investigators one of the engines lost power as he flew into a fog bank.
All three were treated for burns and were flown off the island to mainland hospitals.
Their identities have not been released.
According to a flight-tracking website, the plane had flown in Saturday from San Luis Obispo.
The crash sparked a three-acre grass fire that was put out in about an hour.
