The sheriff's department said the boats - one northbound and carrying 10 people and the other southbound and occupied by six people - collided head on.
The head-on collision of two recreational boats on the Colorado River Saturday has left four people missing and 12 others injured. Immediately after the collision, people on passing boats helped pull victims from the river water.
Mohave County Sheriff's Office search and rescue boats look for four people missing on the Colorado River, north of Lake Havasu in Arizona, on September 2, 2018.
All 16 were thrown into the fast-moving river as the two boats sank.
Ten of the people aboard the boats were hurt, including one critically injured woman who was flown from the scene to a Las Vegas hospital. Nine others were taken to local hospitals by ambulance.
Anita Mortensen, a sheriff's spokeswoman, said Monday that investigators had not determined what role speed might have played in the accident.
The crash happened in Moabi Regional Park, a popular water recreation area along the border about 290 miles east of Los Angeles. The river's water can range from shallow to 30 feet deep.
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Mohave County, which borders the Colorado River, is a county in Arizona.
On Saturday night, authorities had to suspend the search because it was too unsafe to put divers into the dark waters.
"We haven't come up with anything on contributing factors yet", she said, adding that efforts are focused on finding the missing boaters.
Furthermore, Sheriff Doug Schuster said that none of the boaters were wearing life vests, which are not required by law.
Lewis' body was recovered Monday in the river, where three people are still missing after the crash Sunday, the Associated Press reported.
He says two people are missing and "presumed submerged".
The water carried all of them some distance down the river, some as far as three to five miles from the site of the collision.