MOABI REGIONAL PARK, Calif. — Two recreational boats collided head-on Saturday in a stretch of the Colorado River marking the California border with Arizona that was crowded with people enjoying the Labor Day weekend, sinking one boat and leaving 13 people injured, authorities said.

Another four people were missing.

READ MORE: Gov. JB Pritzker Issues New Mask Mandate For Illinois Schools, Some State Employees As COVID-19 Cases Continue To Climb

None of the boaters were wearing life vests when the collision occurred, said Anita Mortensen, a spokesperson for the Mohave County Sheriff’s Office.

The crash happened in Moabi Regional Park, a popular water recreation area along the border about 290 miles east of Los Angeles.

Eric Sherwin, spokesman for the San Bernardino County Fire District, said one person sustained life-threatening injuries and was transported to University Medical Center in Las Vegas. Nine others were transported to local hospitals with less serious injuries. Another six had minor injuries and only one of them requested to go to a hospital.

Sherwin said the depth of the water on the river can range from shallow to 30 feet deep. Rescuers had to call off the search for the missing until Sunday morning because it was too dangerous to put divers in the flowing water after dark.

Some of those onboard the boats apparently were thrown into the water by the force of the collision or jumped, and were swept down the river.

READ MORE: Chicago House Music DJ And Producer Paul Johnson Dies After Battle With COVID-19

“We had victims of this collision that were located 3 to 5 miles downstream from the original point of impact,” said Sherwin.

Sonar of the submerged boat did not appear to show either of the missing persons on board, he said. The other boat was badly damaged by the impact but remained afloat.

Other recreational boats converged on the scene and downstream to help rescue victims, said Sherwin.

 

MORE NEWS: Woman Pistol-Whipped On CTA Blue Line Train In Bucktown

© 2018 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.