Mount Ontake, Japan (CNN) -- At least 31 people are presumed dead after rescuers found them showing no signs of life Sunday near the summit of a Japanese volcano that started erupting a day earlier. 
 
 Police said the people were in a state of "cardiac arrest," meaning that they were discovered without a pulse and weren't breathing but hadn't been declared dead by a doctor. 
 
 A coroner confirmed the first four deaths Sunday. 
 
 Rescue teams had begun searching Sunday for dozens of climbers who were caught by the sudden eruption of Mount Ontake. 
 
 The volcano in central Japan unleashed a huge cloud of ash late Saturday morning that billowed down the mountainside and engulfed hikers in its path. Witnesses described hearing a sound like thunder when the eruption began. 
 
 The exact number of people unaccounted for was unclear, as officials were uncertain how many had already made it off the mountain. 
 
 Desperate relatives 
 
 Relatives of the missing gathered near Mount Ontake on Sunday desperately seeking information. Among them was Kiyokazu Tokoro from nearby Aichi prefecture, whose son, Yuki, was hiking on the volcano with his girlfriend. 
 
 He said he knew they were near the summit at the time of the eruption because his son's girlfriend had sent a photo to a friend minutes beforehand. 
 
 "All I can do is beg for your help to get information," he told CNN. "Please help us." 
 
 Authorities estimated there were 200 to 250 hikers in the area at the time of the eruption. Most of them were reported to have managed to make the long trek down the mountain. 
 
 But some people remained trapped in several lodges on Mount Ontake, and others were missing altogether, local authorities said. 
 
 More than 350 rescue workers -- a mix of police, firefighters and military personnel -- began climbing two separate routes up the mountain on Sunday morning, authorities in the nearby village of Otaki said. 
 
 Alert level raised 
 
 Aside from those in cardiac arrest, more than 25 people were reported to have been injured, 10 of them seriously, according to the government of Nagano prefecture, where the volcano is situated. Helicopters ferried some injured people off the mountainside. 
 
 Among the climbers trapped in the cottages, at least 11 were injured, officials in Otaki said. They said they had observed 17-20 inches (40-50 centimeters) of volcanic ash covering the ground in some areas. 
 
 The Japan Meteorological Agency has raised the Volcanic Alert Level for Ontake from 1 to 3. That means the public is advised to not approach the volcano, the summit of which is at an altitude of 10,060 feet (3,067 meters). 
 
 The agency warned that another large eruption could take place in the next six days or so. Small continuous eruptions continued Sunday. 
 
 The volcano's plume of smoke and ash was reported to have disrupted air travel in Japan, causing delays at several airports. 
 
 Popular destination 
 
 Mount Ontake, the second tallest volcano in Japan, after Mount Fuji, is a popular destination for hikers, especially in the fall when the foliage's rich autumn colors are on display. 
 
 About 250 people living near the mountain have decided to remain in their homes, police said. 
 
 The last major eruption of Mount Ontake, which is about 125 miles (200 kilometers) west of Tokyo, took place in 1979, according to the Global Volcanism Program at the Smithsonian Institute. 
 
 That eruption lasted months, spewing out more than 200,000 tons of ash, the Japanese news agency Kyodo reported. 
 
 Smaller scale activity was reported in 1984, 1991 and 2007. 
 
 CNN's Will Ripley reported from Mount Ontake, and Jethro Mullen reported and wrote from Hong Kong. CNN's Junko Ogura contributed to this report. ||||| KISO, Japan (AP) — Five more bodies were found near the summit of a Japanese volcano on Monday, bringing the total presumed dead to 36, police said, as toxic gases and ash from the still-erupting mountain forced rescue workers to halt efforts to recover the victims. 
 
 CORRECTS DATE - Firefighters and members of the Japan Self-Defense Forces descend Mount Ontake after they called off a search operation due to noxious fume in central Japan, Sunday, Sept. 28, 2014. Mount... (Associated Press) 
 
 CORRECTS DATE- Firefighters and members of the Japan Self-Defense Forces descend Mount Ontake after they called off a search operation due to noxious fume in central Japan, Sunday, Sept. 28, 2014. Mount... (Associated Press) 
 
 An aerial view shows rescue workers searching for missing people in the erupted Mount Ontake, central Japan, Monday, Sept. 29, 2014. Japanese soldiers managed to bring down eight more bodies by helicopter... (Associated Press) 
 
 An aerial view shows rescue workers searching for missing people near mountain lodge with heavily damaged roof top in the erupted Mount Ontake, central Japan, Monday, Sept. 29, 2014. Japanese soldiers... (Associated Press) 
 
 Eight more bodies were airlifted off Mount Ontake before work on the ash-blanketed peak was called off around 1:30 p.m., said Naofumi Miyairi, a spokesman for the Nagano prefecture police. 
 
 Together with four victims brought down on Sunday, 12 bodies have now been recovered, leaving 24 near the summit. Exactly how they died remains unclear, whether from gases, suffocating ash, falling rocks or other causes. 
 
 Police said the latest victims were found near a shrine at the summit, the same area where other victims were reportedly found. 
 
 Japanese TV network TBS showed soldiers carrying yellow body bags one-by-one to a military helicopter that had landed in a relatively wide-open area of the now bleak landscape, its rotors still spinning. 
 
 The bodies were flown to a nearby athletic field, the surrounding forested hills contrasting with Mount Ontake's ash-gray peak in the background, a reduced plume still emerging from its crater. 
 
 The bodies were then taken to a small wooden elementary school in the nearby town of Kiso, where they were being examined in the gymnasium. 
 
 Family members of the missing waited at a nearby municipal hall. 
 
 More than 200 soldiers and firefighters, including units with gas detection equipment, were part of the search mission near the peak, said Katsunori Morimoto, an official in the village of Otaki. 
 
 The effort was halted because of an increase in toxic gas and ash as the volcano continued to spew fumes, he said. 
 
 "It sounds like there is enormous ash fall up there," he said. 
 
 The rescuers reported a strong smell of sulfur, Morimoto said. 
 
 Saturday's eruption was the first fatal one in modern times at the 3,067-meter (10,062-foot) mountain, a popular climbing destination 210 kilometers (130 miles) west of Tokyo. An eruption occurred in 1979, but no one died. 
 
 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 50 centimeters (20 inches) deep. 
 
 The mountain 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. 
 
 Hundreds were initially trapped on the slopes, though most made their way down by Saturday night. 
 
 About 40 people who were stranded overnight came down on Sunday. Many were injured, and some had to be rescued by helicopters or carried down on stretchers. 
 
 Japan's Fire and Disaster Management Agency tallied 40 people who were injured, including three seriously, and said it was trying to determine if any people were still missing. 
 
 Survivors told Japanese media that they were pelted by rocks from the eruption. One man said he and others went into the basement of a lodge, fearing that the rocks would penetrate the roof. He said he covered himself with a thin mattress for protection. 
 
 ___ 
 
 Associated Press writers Mari Yamaguchi and Ken Moritsugu in Tokyo contributed to this report.
– The presumed death toll in the eruption of a Japanese volcano has hit 36 after five more bodies were discovered today, the AP reports. They were found near a shrine at the summit, officials say. Twelve bodies have been airlifted down the mountain, but 24 are believed to remain, and officials have paused recovery efforts amid a continuing threat from toxic gases and ash at the still-rumbling volcano. Some victims were found under 20 inches of the debris, officials say. Reuters puts the number of injured at 63, with eight missing. It was Mount Ontake's first fatal eruption in the modern era, the AP notes. A minor eruption occurred in 2007 and a major one in 1979, though there were no fatalities in that case, Reuters reports. The latest blast was particularly tough to predict, an expert says, despite recent rumblings in the area. "They often occur quite suddenly and there is absolutely no guarantee that … earthquakes earlier this month were connected," he told reporters yesterday. "There is no guarantee of total safety when you're dealing with nature."