The U.S. Coast Guard and Navy were searching for as many as nine people off the Southern California coast following a collision between a Coast Guard plane and a Marine Corps helicopter, officials said.

The crash was reported at 7:10 p.m. on Thursday, about 80 kilometres off the San Diego County coast and 24 kilometres east of San Clemente Island, Coast Guard spokeswoman Petty Officer Allyson Conroy said.

A pilot reported seeing a fireball near where the aircraft collided, Federal Aviation Administration spokesman Ian Gregor said, and the Coast Guard informed the FAA that debris from a C-130 plane had been spotted. Seven people were on board the plane, and two people were aboard the helicopter, he said.

Cpl Michael Stevens, a spokesman for the Miramar Marine Corps Air Station, said the AH-1W Super Cobra helicopter was on a training mission when it went down. The Cobra and its crew are part of Marine Aircraft Group 39, based at Camp Pendleton, and the 3rd Marine Aircraft Wing, which is headquartered at Miramar, Stevens said.

The missing Coast Guard plane and its crew are from Coast Guard Air Station Sacramento, said Coast Guard Petty Officer 2nd Class Jetta Disco. Crews from the Sacramento Coast Guard station fly search-and-rescue, law enforcement and logistics missions, Mr. Disco said.

The Coast Guard planned to search through the night, having sent three cutters and diverting an MH-60 Jayhawk helicopter to the area to search for survivors. The Navy, meanwhile, sent four vessels and multiple helicopters.

“The search conditions are ideal for tonight,” Lt. Josh Nelson of the Coast Guard told XETV in San Diego. “We’ve got a clear sky, the winds are calm, the seas are calm, and we have a lot of assets out there.”

Meanwhile, stormy weather forced the Coast Guard to suspend its search for two missing Navy pilots and their plane along the central Texas coast.

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