Authorities say three women riding on a personal watercraft were killed when they crashed into a motorboat at a Southern California reservoir.

Los Angeles County fire Inspector Matt Levesque (luh-VECK') said the Saturday collision at Puddingstone Lake also left three men from the boat with serious injuries and a woman with minor injuries. They are all expected to survive.

Authorities say the women, ages 25, 35, and 60, were all riding on the same Sea-Doo watercraft when they crashed. Paramedics declared all three dead at the scene.

Sheriff's homicide detectives and county lifeguards are investigating the crash, but have not said what may have caused it.

Puddingstone is a popular recreational reservoir inside Frank G. Bonelli Regional Park, some 30 miles east of downtown Los Angeles.