Los Angeles, Sep 3 (IANS): Four persons have gone missing and nine others have been injured after two boats collided on the Colorado river bordering the US states of California and Arizona, authorities said. A search is on.

The collision occurred about 8 p.m. on Saturday between Pirates Cove and the Topock Marina near Moabi Regional Park on the California-Arizona border, authorities said.

Search-and-rescue divers were in the water searching for bodies all through Sunday.

The search will again resume on Monday, L.A Times quoted Mohave County Sheriff's Office in Arizona as saying.

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

The river was packed with holiday visitors at the time of the incident. Those aboard the boats were friends and family. None of them were wearing life jackets, he said.

All passengers were ejected into the water after a northbound Hallet craft carrying 10 people collided head on with a southbound Sleek Craft boat with six people on board. Both vessels sank later, Xinhua news agency reported.

"Two of the nine injured are critical," Schuster said. A probe is on. Divers will again scour the waters on Monday. All vessels have been asked to keep clear of the area.

The Moabi Regional Park is a resort for water recreation and beautiful scenery.