The seven are in addition to the 36 already known to have died when Mount Ontake burst angrily to life during the busy hiking season, but may not be the last, with reports of more bodies lying near the peak.

"Rescuers found seven more people in cardiac arrest near the mountain top, and are now carrying them down," an official in Otaki village, where one mountain trail begins, said.

Only doctors can declare someone officially dead, so first responders typically report that someone's heart has stopped and they are not breathing.

The find comes after media reports suggested as many as 20 people remain unaccounted for, with an area of the volcano still out of bounds to rescuers as it continues to billow toxic gas and steam.

Some of the troops, police and firefighters combing the volcano succeeded in bringing down 14 of the bodies that were discovered on Sunday, with 10 more still there.

An official at Nagano prefecture's crisis management office said helicopters had been used to ferry the dead from the mountain, whose pock-marked lunarscape bears witness to the huge volume of ask and rocks that were flung from the volcano.

"We believe there are more people still missing, but we don't know how many they are," he added.

Broadcaster NHK said rescuers had seen more bodies that they had not yet been able to go to.

Hiking is an incredibly popular pastime in Japan, with mountain trails promoted by tourism officials who ask walkers to sign in when they begin their trek and sign out again when they finish.

But a local tourism association said "usually only 10 to 20 percent of hikers register their names with authorities before entering the mountains in high season".

The report said 327 hikers had registered to be on Mount Ontake at the time of the eruption.

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