A U.S. Air Force B-52 Stratofortress bomber crashed shortly after takeoff at Edwards Air Force Base in California on Monday, the Pentagon said.

Air Force Secretary Troy Meink said in post on X that the eight people aboard were killed.

The aircraft had been on a ¡°routine test mission¡± when the crash occurred at 11:20 a.m. Pacific Standard Time, according to a statement from Edwards Air Force Base, which added that an investigation regarding the cause was underway.

¡°We are deeply saddened by the eight lives lost in today¡¯s tragic crash at Edwards AFB,¡± Meink said in a post on X Monday night. ¡°We mourn this loss and honor the service of our Airmen, civilians, and contractors who work every day to advance our mission. I send my sincerest condolences to their families and loved ones.¡±

The long-range Boeing?bomber typically carries five crewmembers?and has been operated by the Air Force since the 1950s. The aircraft cost around $84 million, according to an Air Force fact sheet.

The bombers played a key role in Operation Desert Storm in the early 1990s and were recently deployed in operations against Iran, helping to strike key targets like air defense systems and command posts.