LAS VEGAS (KLAS) — A man was flown to a Las Vegas hospital for treatment of serious injuries after two boats collided on the Colorado River on Tuesday, according to the Mohave County Sheriff’s Office (MCSO).

The man was one of four people injured in the crash. All of them were transported to Havasu Regional Medical Center, according to information provided on the MCSO’s Facebook page. The man was then sent to Las Vegas for treatment.

The two boats — a 21-foot Aftershock and a 20-foot Eliminator — collided when one tried to pass the other where the river meets the north basin of Lake Havasu.

“After colliding, the Aftershock Boat ramped over the top of the Eliminator boat, and struck both of the boat’s occupants,” according to MCSO’s report, which said the Aftershock had tried to pass the Eliminator. Photos provided by the sheriff’s office showed damage to the front of the Eliminator.

MCSO deputies took two male occupants with “significant injuries” from the Eliminator to medical personnel waiting on shore. The Lake Havasu City Fire Department responded and transported two occupants of the Aftershock to shore. They had minor injuries.

The incident is still under investigation. Alcohol does not appear to be a factor.