There was no immediate word on casualties.

The crash happened around lunchtime at the base, a major operations center for the US military around 60 miles (95 kilometers) north of Los Angeles.

"A United States Air Force B-52 Stratofortress crashed shortly after takeoff on the Edwards airfield at 11:20 am," the base said on Facebook.

"Emergency crews immediately responded to the scene and the situation is ongoing.

"The airfield has been closed, and all inbound aircraft are being diverted. Additionally, all non-commercial visitor passes have been suspended until further notice to allow the installation to focus entirely on emergency response operations."

A spokesman from the base declined to give any further information.

Aerial footage showed a huge charred area on the ground.

There appeared to be very little left of the plane, with a journalist in a broadcast helicopter speaking of a "large plume" of black smoke that had been visible in the aftermath of the crash.

A number of emergency vehicles could be seen by the burned patch.

The B-52 is a heavy bomber that first flew in 1954 and was originally designed for war with the Soviet Union. It has received continual upgrades to keep it in service for decades since the Cold War's end.

The massive bomber -- which can carry a range of weapons, including bombs and cruise missiles -- has a wingspan of 185 feet (56 meters) and a length of 159 feet (48 meters).

The plane is usually crewed by five people: an aircraft commander, a pilot, a radar navigator, a navigator and an electronic warfare officer, according to a US Air Force fact sheet on the plane.

With a combat range of up to 8,800 miles the plane is capable of carrying a nuclear payload.

The United States has deployed the aircraft in conflicts in Vietnam, the Gulf, Iraq, Afghanistan, and most recently in Iran.