Rescue workers continued their search for survivors on Monday, two days after a large mudslide in a hot spring resort town southwest of Tokyo killed at least four people and destroyed no fewer than 130 houses.

Firefighters, police and Self-Defense Forces personnel continued to remove debris and search mud-swamped houses in Atami, Shizuoka Prefecture, as the first 72 hours after the incident, considered a crucial period for finding survivors, neared.

A man (L) watches rescue workers searching for missing people on July 5, 2021, at the site of a large mudslide triggered two days ago by torrential rain in the Shizuoka Prefecture hot spring resort city of Atami, southwest of Tokyo. (Kyodo) ==Kyodo

On Monday, the rescue team found three people who had been missing, one of whom was confirmed dead, the city government said. The remaining two were reportedly not in a life-threatening condition.

The municipality is continuing its efforts to locate 64 people whose whereabouts are still unknown based on the basic resident register. The figure may include those who had already moved from the city before the disaster but are listed on the resident list.

The city government has identified one of the four dead as 82-year-old Chiyose Suzuki, but the three other victims including two women are yet to be identified.

Suzuki's eldest son Hitoshi, 56, told Kyodo News he regrets not bringing his mother, who could not walk well, with him when they were urged by police to evacuate.

"I should have gone back and taken her out there myself" instead of leaving her behind before rescuers arrived for assistance, he said.

His mother died shortly after he rejoined her at hospital.

Search and rescue operations continue for missing people in the Shizuoka Prefecture hot spring resort city of Atami, southwest of Tokyo, on July 5, 2021, two days after torrential rain triggered a large mudslide. (Kyodo) ==Kyodo

In Tokyo, the Imperial Household Agency said Emperor Naruhito and Empress Masako are deeply distressed by the deaths and people who remain unaccounted for in the area hit by the mudslide.

Prime Minister Yoshihide Suga told reporters in the capital that rescuers will continue looking for those believed to be buried in the mud.

Suga instructed members of his Cabinet to "save as many lives as possible and do your utmost to quickly make rescue efforts and support victims" at a disaster management task force meeting in the morning.

The top government spokesman Katsunobu Kato said the state will team up with experts and the Shizuoka prefectural government to look into whether the massive mudslide was exacerbated by about 54,000 cubic meters of soil which was accumulated at the mountain.

The city government said the former land owner, a Kanagawa-based real estate company, left the soil there in 2007. The local authorities suspect that some 100,000 cubic meters of soil, including the accumulated soil, collapsed into a nearby river around 10:30 a.m. Saturday, and traveled a distance of about 2 kilometers.

Search and rescue operations continue for missing people in the Shizuoka Prefecture hot spring resort city of Atami, southwest of Tokyo, on July 5, 2021, two days after torrential rain triggered a large mudslide. (Kyodo) ==Kyodo

Shizuoka Gov. Heita Kawakatsu inspected the disaster-hit area and told reporters, "Due to the accumulation of prolonged rain, the soil (left by the company) and sediment were washed away and exacerbated the damage."

While accumulated soil is generally looser than naturally-formed mounds, Michiya Irasawa, a professor of erosion control at Iwate University, said that such soil would still usually stay in place if compacted with heavy machinery.

"I suspect a large volume of water flowed inside the mound and weakened its hold," he said.

Norifumi Hotta, an associate professor of erosion control engineering at the University of Tokyo, said the collapse of the accumulated soil may have triggered the mudslide.

With the site originally at risk, he called for an investigation into whether leaving such a large amount of soil there was appropriate.

The local government closed 11 elementary and junior high schools, and four kindergartens on Monday as warnings against heavy rain and mudslide remained in place.

On social media platform Twitter, people posted the names, ages, descriptions and photos of missing relatives.

Among those searching for their relatives is 71-year-old Koichi Tanaka, whose 70-year-old wife Michiko went missing after Tanaka left his wife at home to check on her friend.

"I cannot believe that the city's face changed drastically within an hour," said Tanaka.

A local arm of the Japan National Council of Social Welfare began the enrollment of volunteers on Monday, but only taking on workers from within the prefecture as a measure against the coronavirus.

The start of volunteering is expected to be delayed for the time being due to fears of a secondary disaster.

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2 dead, some 20 missing in large mudslide southwest of Tokyo