SAUSALITO -- A boater suffered burns over 30 percent of his body after a sudden explosion caused the watercraft to become engulfed in flames in the Sausalito harbor, authorities said.

The unidentified man had to dive into the chilly bay waters to escape the fire Sunday night and was rescued by neighboring boat owners, Marin County fire officials said.

He was examined on a fireboat and later hospitalized with moderate burns. The man's name was not released, and officials said they did not know whether he was the boat's owner.

Officials are still investigating what caused the explosion on the 35-foot vessel. They speculate it might have been caused by fuel that ignited and burned quickly. The boat was totaled.