It was not immediately clear what caused the crash, and it could take up to six months to complete an investigation, Col. James Hayes said.

Edwards Air Force Base said emergency responders were on the scene.

Officials say a B-52 bomber crashed shortly after takeoff at a U.S. Air Force base in California's Mojave Desert.

An official said an investigation could take up to six months and noted the B-52 in question was involved in a "radar modernization program."