WASHINGTON — A US Air Force B-52 Stratofortress bomber crashed today after taking off from Edwards Air Force Base in California, and “initial indications” show the mishap was “not survivable” for eight people on board the aircraft, according to military authorities.

“Emergency personnel are on scene, and officials are working to account for all personnel,” Edwards Air Force Base said in a statement.

Boeing, the prime contractor for the Stratofortress, said in a statement this evening that two company employees were on board the B-52 that crashed.

“We extend our deepest condolences to the loved ones of the eight crew members who lost their lives” in the incident, the company said.

The incident occurred around 11:20 am local time during a “routine test mission,” the Edwards Air Force Base statement said. The installation is located in the desert north of Los Angeles.

The B-52 is a long-range, swept-wing bomber that entered service in the 1950s. The Air Force is upgrading the bomber’s engines, radar and other subsystems to extend its service life into the 2050s.

Edwards Air Force Base is a testing hub, where officials can evaluate upgrades and the integration of new weapons.