"They were all covered with ash, completely white"

TOKYO - Rescue workers say at least 31 people are believed to been killed by an erupting volcano in central Japan.

Nagano prefecture posted on its website that about 31 people had heart and lung failure, the customary way for Japanese authorities to describe a body until police doctors can examine it. At least four of the victims were being brought down from Mount Ontake on Sunday afternoon, one day after the volcano erupted.

Public broadcaster NHK and the Kyodo news agency later reported that four, all male, had been confirmed dead, according to Reuters.

It was the first fatal eruption in modern times at 10,062-foot Mount Ontake, a popular climbing destination about 130 miles west of Tokyo on the main Japanese island of Honshu. A similar eruption occurred in 1979, but no one died.

Rescue helicopters hovered over ash-covered mountain lodges and vast landscapes that looked a ghostly gray, like the surface of the moon, devoid of nearly all color but the bright orange of rescue workers' jumpsuits.

Japanese media reported that some of the bodies were found in a lodge near the summit and that others were buried in ash up to 20 inches deep. Police said only two of the four confirmed dead had been identified. Both were men, ages 23 and 45.

Mount Ontake erupted shortly before noon at perhaps the worst possible time, with at least 250 people taking advantage of a beautiful fall Saturday to go for a hike. The blast spewed large white plumes of gas and ash high into the sky, blotted out the midday sun and blanketed the surrounding area in ash.

Mount Ontake in central Japan erupted shortly before noon Saturday, spewing large white plumes of gas and ash high into the sky and blanketing the surrounding area in ash. The mountain is a popular climbing destination, and at least 250 people were initially trapped on the slopes, though most made their way down by Saturday night.

"The volcanic rocks fell like hailstones," one survivor said, according to the BBC. "We couldn't breathe so we covered our mouths with towels. We couldn't open our eyes either."

In a video posted on YouTube, shocked climbers can be seen moving quickly away from the peak as the expanding ash plume emerged above and then engulfed them.

Before the unconscious victims were found, Japan's Fire and Disaster Management Agency said that 45 people had been reported missing. The exact location of the bodies and their identities were not immediately known.

Keita Ushimaru, an official in nearby Kiso town, said that Nagano crisis management officials had informed the town that at least four people with heart and lung failure were being brought down to the town, and that there were others in the same condition. The journey was expected to take about three hours.

Rescue workers were also trying to help injured people and others who had been stranded on the mountain overnight, many taking refuge in mountain lodges. Some were unable to descend on their own, or unwilling to take the risk.

Military helicopters plucked seven people off the mountainside earlier Sunday, and workers were helping others make their way down the slopes. One woman was being carried on a stretcher, and a man with a broken arm was walking down.

Seven people were picked up in three helicopter trips, said Defense Ministry official Toshihiko Muraki. All are conscious and can walk, though details of their conditions were unclear, he said.

Japanese television footage showed a soldier descending from a helicopter to an ash-covered slope, helping latch on a man and then the two of them being pulled up.

The Self-Defense Force, as Japan's military is called, has deployed seven helicopters and 250 troops. Police and fire departments are also taking part in the rescue effort.

A large plume, a mixture of white and gray, continued to rise from the ash-covered summit of 10,062-foot Mount Ontake on Sunday, visible from the nearby village of Otaki. A convoy of red fire trucks, sirens blaring, and rescue workers on foot headed past barriers into the restricted zone around the mountain.

Shinichi Shimohara, who works at a shrine at the foot of the mountain, said he was on his way up Saturday morning when he heard a loud noise that sounded like strong winds followed by "thunder" as the volcano erupted.

"For a while I heard thunder pounding a number of times," he said. "Soon after, some climbers started descending. They were all covered with ash, completely white. I thought to myself, this must be really serious."

A worker in a mountain lodge just below the peak, Shuichi Mukai, told Sky News: "All of a sudden ash piled up so quickly that we couldn't even open the door. We were really packed in here, maybe 150 people. There were some children crying, but most people were calm. We waited there in hard hats until they told us it was safe to come down."

To watch aerial footage of the erupting volcano click on the video player below.

Mount Ontake, about 130 miles west of Tokyo, sits on the border of Nagano and Gifu prefectures, on the main Japanese island of Honshu. The volcano's last major eruption was in 1979.