NAGANO - Rescuers continue to search Mt. Ontake for the remaining missing hikers, but already difficult conditions could worsen as a typhoon and the snowy season approach. As of Friday, there were 55 confirmed deaths caused by the mountain's eruption two weeks ago.
Rescuers did not locate any of the missing on Friday, with one senior Metropolitan Police Department official describing the deep layer of volcanic ash as a "bottomless swamp."
On Tuesday, rescue squads began using a "roller strategy" in which rescuers spread out in a line. Previously they had focused on areas near the hiking trails.
There were about 550 rescuers on the mountain on Friday, the largest number so far, using the roller technique to search a section that had not yet been explored. In a depression north of the summit called Ichinoike pond, rescuers formed a line about 500 meters long to search the area, including swampy places that had not been combed.
Some personnel sank up to their chest or waist, so they tried using the duralumin shields used by riot police to disperse their weight.
"We made a lot of preparations and gathered a lot of information, but we didn't imagine the mud would be this bad," said a 50-year-old vice chief of the MPD's fourth riot police squad. "It's like concrete or mortar beginning to solidify."
The air is thin and cold on top of the 3,000-meter mountain, and at least five rescuers are said to have developed hypothermia or altitude sickness. In some areas, the volcanic ash has hardened.
A 35-year-old chief of the Matsumoto squad of the Kanto district riot police, worked near Ninoike, the mountain's crater pond, and the Haccho-darumi trail.
"It's becoming more difficult to search by digging into areas with our hands or poles," he said.
Much of the site is steep and rocky, and areas such as around the crater are particularly dangerous, prompting Nagano Prefecture and other authorities to create no-entry zones.
Friday's search did not discover any bodies. Although the day's efforts meant the entire area has been covered, places with deep ash or steep cliffs were difficult to search properly, so victims may have been overlooked.
The plan for Saturday was to focus on an area within a one-kilometer radius of Kengamine, the mountain's highest point. With typhoon No. 19 on the way, Hayashi said, "We want to search as much as we can before the weather, toxic gas or other conditions worsen."
According to authorities in Kiso, Nagano Prefecture, the first snow fell on Mt. Ontake on Oct. 6 last year.
"When the temperature rises in winter, there could be flows of volcanic ash mixed with snow, or snow sitting on top of the ash could come down in avalanches," said Hiroki Matsushita, head researcher at the Snow Avalanche and Landslide Research Center, an independent administrative agency based in Myoko, Niigata Prefecture.