A B-52 bomber of the US Air Force crashed shortly after takeoff from Edwards Air Force Base in California’s Mojave Desert on Sunday, killing all eight crew members on board.

The aircraft, which was on a routine test mission, took off at approximately 11:20 am (local time) before going down near the remote military installation northeast of Los Angeles. Media reports said thick black smoke was seen rising from a large patch of scorched desert near the runway, with emergency vehicles rushing to the site.

All eight crew members are presumed dead, and the operation has shifted from rescue to recovery, CNN reported.

Colonel James Hayes, deputy commander of the 412th Test Wing at Edwards, said at a press briefing that, after reviewing crash footage, officials concluded that no one could have survived.

“We lost eight great Americans,” Hayes said, adding that authorities were in the process of notifying the families of the deceased.

The cause of the crash is not yet known, and investigators said it could take up to six months to determine what went wrong. Aviation experts suspect some kind of flight control malfunction.

"It's possible the controls were rigged wrong after maintenance or a catastrophic engine problem or a failure of a piece of equipment that was being tested," aviation safety expert Jeff Guzzetti told the Associated Press.

"I think it was definitely a controllability issue. Now, whether that was tied to an engine failure, a flight control failure, or some new testing device failure, I'm not sure," he said.

According to Air Force officials, the aircraft was conducting a test mission in support of a radar modernisation programme when the accident occurred.

Operations at Edwards Air Force Base have been suspended through Tuesday as authorities continue recovery efforts and investigate the wreckage. The base is a major hub for US Air Force flight testing and development.

The Boeing B-52 Stratofortress is one of the oldest aircraft still in active US Air Force service. First introduced in 1955, the long-range heavy bomber is capable of carrying both conventional and nuclear weapons and has been deployed in conflicts ranging from Vietnam to Iraq.

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