Ten people have been injured and four others are missing after two private boats collided head-on in southern California.
One of the vessels sank while the other suffered major damage but remained afloat following the crash on the Colorado River on Saturday.
The missing are "presumed submerged".
One person was airlifted to the University Medical Centre of Southern Nevada with life-threatening injuries.
Nine others had to be taken to hospital.
Some of those on board the boats were thrown into the water by the force of the collision or jumped, and were swept down the river.
"We had victims of this collision that were located three to five miles downstream from the original point of impact," said Eric Sherwin, a spokesman for the San Bernardino County Fire District.
Rescuers had to call off the search for the missing until Sunday morning because it was too dangerous for divers to swim in the river after dark.
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The smash happened in Moabi Regional Park, a popular water recreation area situated about 290 miles east of Los Angeles.
The stretch of river along the California-Arizona border where the collision took place had been crowded with people enjoying the Labor Day weekend.
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