Colorado River Boat Crash Latest: Search on for Survivors North of Lake Havasu

The search continues for four people who are missing after two boats collided with each other and sank on the Colorado River.

A total of 16 people were on the boats when they crashed into each other just after 8 p.m between Pirates Cove and the Topock Marina, north of Lake Havasu on September 1.

All 16 people were thrown into the water following the collision, with several being pulled out of the water by passing boaters after both of the vessels sank.

Nine people were injured in the crash—two of them critically—with one male and three females still unaccounted for, the Mohave County Sheriff's Office said in a statement.

A huge search was launched along the stretch of river, including divers looking for bodies in the water.

"I don't want to give the interpretation that there isn't a real possibility that they made it to shore," Mohave County Sheriff Doug Schuster told a news conference. "We are actively treating this as a potential drowning."

Authorities are still trying to determine what caused the crash. So far, it has been determined that a Hallet boat carrying 10 people was travelling northbound, and a Sleek Craft boat, occupied by six people, was heading southbound.

Authorities search for four people who went missing after two boats collided and sunk on the Colorado River. Mohave County Sheriff’s Office

"At this time, four occupants from the Hallet boat are still missing," the Mohave County Sheriff's Office said. "Helicopters from Care Flight, Arizona DPS Air Rescue, and the San Bernardino County Sheriff's Department were deployed in the area shortly after the initial call, and were unable to locate any of the missing subjects."

Authorities believe that low light may have been a factor in the crash and are looking into how fast either of the boats were traveling at the time. According to a transcript of the 911 call, both boats were traveling at speeds of up to 50 miles an hour, reports 3TV/CBS 5.

Schuster confirmed that no one on either boat was wearing life jackets at the time.

"It is not mandated that they do, though we encourage it," he told reporters.

Eric Sherwin, a spokesman for the San Bernardino County Fire District, told 3TV/CBS-5 that the fast moving river is causing problems for the search operation.

"We had victims of this collision that were located three to five miles downstream from the original point of impact," Sherwin said.

Mohave County Sheriff's Office confirmed the river has been closed to the public while the search continues.

Colorado River Boat Crash Latest: Search on for Survivors North of Lake Havasu | U.S.