The unexpected eruption of a volcano in a popular upland tourist district sent authorities scrambling to get word to tourists and residents on Thursday.
Mount Asama spewed smoke and ash for about 20 minutes the previous evening. It last erupted in 2015, and was on the Meteorological Agency’s lowest alert level.
One of Japan’s most active volcanos, the cone-shaped mountain towers over popular summer retreats such as Karuizawa in Nagano and the village of Tsumagoi in Gunma. The eruption at 10:08 p.m. Wednesday at a location near the crater sent smoke to an altitude of about 1,800 meters, according to the agency. The 2,568-meter-high volcano sits on the border of Nagano and Gunma prefectures.
There were no reports of injuries nor property damage as of Thursday morning.
The small eruption prompted the volcanic alert level to be raised from 1 to 3, on a scale of 5. The elevated alert level means people should not approach the mountain.
The agency warned of possible flying rocks and pyroclastic flows within 4 km of the crater.
Communities at the foot of the volcano rushed to take safety steps.
The Nagano Prefectural Government said two trails up Mount Asama were closed off. Cars were temporarily banned from entering the Onioshi Highway, a scenic road that winds near the volcano and connects the Nagano side with Gunma, before the all-clear was given Thursday morning.
The town of Naganohara in Gunma advised 28 people at a campsite to evacuate. The site is within the 4-km radius.
Nae Nakamura, a 40-year-old housewife from Tokyo whose family evacuated the campsite and spent the night at a community center in Naganohara, said Thursday morning that she was “terrified to see black smoke rising” from the volcano the previous night.
The manager of Takamine Kogen Hotel in Komoro, a city near Mount Asama, said some 50 guests were staying there at the time of the eruption. Cancellation calls are now coming in, he added.
At a news conference early Thursday, the Meteorological Agency said there had been no pyroclastic flows, just ash falling up to 200 meters from the crater. But it urged people to stay out of harm’s way by following instructions from local authorities, as ash could fall on the prefectures of Gunma, Nagano and Niigata.
The government has set up a liaison unit at the central crisis management center, which is administered by the Prime Minister’s Office.
The mountain last erupted in June 2015. The agency lowered the alert level from 2 to 1 in August last year.