A U.S. Marine helicopter crashed on a fog-shrouded hillside Saturday about one mile from a nuclear power plant, killing all seven Marines aboard, military officials said.

The CH-53D Sea Stallion crashed about 10:20 a.m. as it was crossing Shikoku Island in southern Japan shortly after Typhoon Thad swept over the area, triggering landslides that killed four people and injured 16.Police found twisted fragments of the twin-engine medium transport and seven bodies scattered on a hillside orange grove 406 miles southwest of Tokyo.

"Marine Corps officials have confirmed seven people are dead, and names are being withheld pending notification of next of kin," a Marine Corps spokeswoman said.

U.S. military investigators searched through the twisted fragments of the Marine helicopter but were unable to immediately determine a cause of the crash, said police and a Marine spokesman.

The CH-53D is not the helicopter that has been the subject on ongoing controversy about its in-flight performance. Its heavy-cargo sister ship, the three-engine CH-53E, has been involved in seven major accidents that have claimed the lives of 20 servicemen since June 1981.

But Saturday's crash, 1 mile east of the Ikata nuclear power plant, renewed concerns over the safety of nuclear plants built in areas of heavy air traffic.

Residents near the Ikata nuclear plant asked the Japanese courts to stop construction of the plant before it started because of the frequent air traffic in the area.

"It would have been a disaster if the helicopter had crashed on the plant, releasing massive amounts of radioactivity," said Shoichi Kono, chairman of a group opposed to the plant.

But the director of the facility, Kazuhiko Yamashita, said, "The plant is designed in such a way that, even if an aircraft crashes into it, the reactors will be safe."

He added flights directly over the nuclear plant are banned.

Police refused to say if the helicopter was flying in the direction of the plant at the time of the crash.

Meteorologists said visibility at the time was 50 to 60 yards because of heavy fog, and news reports said the helicopter was flying low. Police said the crew sent no distress calls prior to the crash.

The bodies were returned to the Marine Corps Air Station at Iwakuni, 25 miles west of Hiroshima, where the helicopter left at 9:50 a.m. "on a routine flight" to its home base at Marine Corps Air Station Futenma in Okinawa, Sgt. Nolan Wells said.

Wells said the helicopter was assigned to Marine Heavy Helicopter Squadron 462 of the 1st Marine Aircraft Wing.

Three years ago, 17 Marines died when their transport helicopter flying the same route crashed in heavy winds off the coast of Japan.

Typhoon Thad, which turned into a tropical depression about an hour before the helicopter crash, unleashed a downpour Friday and Saturday that flooded 900 homes and caused 156 landslides in southern Japan, the Kyodo news service reported.