The Coast Guard in Honolulu sent a C-130 Hercules with 23 personnel to Sacramento, Calif. to augment the air station there as searchers continue to look for nine people missing in the Thursday collision of a Coast Guard plane and Marine Corps helicopter off Southern California.

The Honolulu C-130 aircraft, one of four at Air Station Barbers Point, touched down in Sacramento at 8:30 a.m. this morning, officials in Hawai'i said.

Chief Petty Officer Chad Saylor, a Coast Guard spokesman, said the Barbers Point C-130 left with two air crews and a maintenance crew.

Investigators are trying to determine why the Sacramento-based Coast Guard C-130 rescue plane on a nighttime search for a boater collided with one of four Marine Corps helicopters flying in formation to a military training island off Southern California.

The collision occurred about 7:15 p.m.

All seven people aboard the Coast Guard plane out of Sacramento and the two-person crew of the Marine Corps AH-1W Super Cobra helicopter were missing. The search is focused on a debris field 50 miles off the San Diego coast.