(August 7, 2008)—Federal investigators were headed to a remote part of a Northern California forest where a helicopter crash may have killed as many as nine people.

Officials say the aircraft had just picked up 11 firefighters who were battling a blaze in the Shasta-Trinity National Forest when the helicopter went down and caught fire Tuesday night.

Three firefighters and a pilot were flown to hospitals with severe burns.

The Trinity County Sheriff's Department is leading the search for crash victims. Eight firefighters and a second pilot remain missing and are feared dead.

The National Transportation Safety Board, which is leading the investigation into the crash, is going to the scene.