Mount Ontake volcano: Most of the dead likely struck by rocks

Doctors have determined that almost all of the dozens of people killed on a Japanese volcano died of injuries from being hit by rocks that flew out during its eruption, police said.

Rescuers have retrieved 47 bodies from the ash-covered summit area of Mount Ontake since Saturday's eruption. Authorities announced Friday that another 16 people are still missing. Search efforts were suspended because of rain.

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Doctors concluded that all but one of the bodies showed signs of having been hit by volcanic boulders and rocks, Nagano prefectural police said. The other victim died of burns from inhaling hot air.

Those hit by the rocks and debris had multiple cuts and fractures, particularly in the head and the back, as well as the legs, a prefectural police official said on condition of anonymity, citing department policy. Nagano police had earlier said the victims died of "disaster," without specifying the cause.

Most of the bodies were found near Mount Ontake's summit, where many climbers were resting or having lunch. Some bodies were retrieved from a trail at a slightly lower elevation.

Japan's deadliest eruption in postwar era

Experts say hikers near the summit might have been hit by rocks flying as fast as 300 kilometres per hour. Most of the ash fell in the first hour of the explosion, according to the University of Tokyo's Earthquake Research Institute.

Medical experts who have examined some of the nearly 70 injured have said most had bruises, cuts and bone fractures on their back, an apparent sign they were hit by rocks flying out of the volcano. Some of the injured reportedly had damage to their lungs and other organs due to the impact of rocks hitting them.

The eruption at Mount Ontake, located in central Japan, caught hikers by surprise. Seismologists have said that increased seismic activity had been detected at Ontake, one of 47 active volcanoes in Japan that are under 24-hour monitoring, but that nothing signalled such a big eruption.

The death toll is the highest from a volcanic eruption in Japan's postwar history, exceeding the 43 people killed in the 1991 eruption of Mount Unzen in southern Japan.