Nine military members are still missing on Friday after a midair collision off the coast of California.

Investigators began the search overnight for those believed to be missing after the Thursday evening crash involving a Coast Guard airplane and a Marine Corps helicopter.

"A tragic event," Pentagon spokesman Bryan Whitman said. "The search is still on, but it's likely taken the lives of nine individuals."

The plane and helicopter collided 50 miles from San Diego, Calif., killing all seven people aboard the C-130. The two passengers of the Marine Corps AH-1W Super Cobra helicopter were also reported missing.

Another pilot reported seeing a fireball near where the crash site is believed to be.

Search teams are scanning an area of debris 644-square-miles near the San Diego coast.