A U.S. military transport plane crashed in central Albania while on a training mission Thursday, and nine American personnel aboard were believed to have been killed, Albanian officials said.

The Pentagon said a search was under way for the C-130 (search) but poor weather was hampering efforts.

The plane had taken off from Tirana's airport and crashed on Driza Mountain in the district of Gramsh (search), 50 miles southeast of capital, Tirana, Albanian Defense Ministry spokesman Agim Doci told The Associated Press.

Doci said officials believe that the nine people aboard, all Americans, were killed.

Pentagon (search) spokesman Jim Turner said he had no word on the crew's status.

Albanian army Chief-of-staff, Lt. Gen. Pellumb Qazimi, said the plane was part of a joint Albanian-U.S. military exercise.

"All the necessary steps have been undertaken and search operations have already started with troops, from the air and to continue at dawn," he said.

The Albanian News24 television station reported that the location of the crash was remote and hard to reach, adding that a helicopter was seen circling the area.

Residents said an explosion caused by the crashing plane felt "like an earthquake," the station said.