Sept 2 (Reuters) - Divers searched the Colorado River in Arizona on Sunday for four people missing after two boats slammed head-on into each other, flinging all aboard into the water, sinking both vessels and injuring nine people, police said on Sunday.
The collision happened on Saturday night near Arizona's border with California when a boat with 10 people and a craft carrying six people collided. Several people were rescued by nearby boaters, the Mohave County Sheriff's Office said.
Divers were set to search up until sundown on Sunday for the four missing, the sheriff's office said.
"This is technically a diving mission looking for potential drowning victims," Sheriff Doug Schuster said at a news conference. He said it was possible that the missing - one male and three females - had made it to the shore.
The cause of the accident was under investigation, Schuster said.
Two people were critically injured in the crash, the sheriff's office said, including one person who was airlifted from the scene with a head injury.
The others aboard the boats were not seriously injured and did not need to go to a hospital, authorities said.
The sheriff's office had previously said 10 people were injured. (Reporting by Jon Herskovitz in Austin, Texas; Editing by Peter Cooney and Bill Trott)