( CNN ) -- Nine people were missing and presumed dead and four were hospitalized Wednesday after a helicopter carrying firefighters crashed the night before in northern California , aviation spokesmen said . The Sikorsky S-61 helicopter entered a remote area to pick up firefighters battling wildfires , said Ian Gregor of the Federal Aviation Administration . The crash happened about 7:30 p.m. Tuesday , 35 miles northwest of Redding in the Trinity Alps Wilderness area of the Shasta-Trinity National Forest . Two crew members and 11 firefighters were aboard , Gregor said . Three of the injured were contract firefighters , and the fourth was the pilot , said Sharon Heywood , the forest 's supervisor . All of the injured initially were taken to Mercy Hospital near Davis , California . A firefighter in critical condition and two people in serious condition -- a firefighter and the pilot -- were transferred to the University of California Davis Medical Center , Heywood said . The third firefighter remained at Mercy in serious condition Wednesday , she said . Heywood said the crash site was difficult to access because of its terrain . U.S. Forest Service spokeswoman Daria Day said the helicopter , assigned to a group of four fires burning in the forest , went down near the north end of the so-called Buckhorn fire . She said she did n't know if the helicopter was landing or taking off . The helicopter was operated by Carson Helicopters , which has offices in Grants Pass , Oregon , and Perkasie , Pennsylvania , according to Sacramento , California , TV station KCRA . `` We do n't know what occurred , '' Carson Helicopters ' Bob Madden told KCRA . `` We have n't examined the aircraft yet . We 've never had a copter go down due to firefighting efforts . '' The crash was being investigated by the FAA and the National Transportation Safety Board , Gregor said . The Buckhorn fire -- part of the Iron Complex fires in the forest -- has burned more than 18,500 acres since it started June 21 , the Forest Service said . It was 25 percent contained Wednesday , according to the service . The four Iron Complex fires have burned more than 84,000 acres since they started on or about June 21 , the service said .
Helicopter carrying 11 firefighters , two fatal crashes in California , officials say . Two firefighters missing and presumed dead . Firefighters had been assigned to fight wildfires . Fire Service reported : Injured four -- including pilot -- hospitalized .