Authorities raised the volcanic alert level for Mount Hakone on Sunday — warning of a possible eruption — after increasing seismic activity was detected near the popular hot-spring resort area in Kanagawa Prefecture.
For the first time since 2015, the Meteorological Agency raised its alert level at the site to a 2 on the 5-point scale, meaning people have been barred from approaching the crater.
The agency said it decided to raise the level from 1 after the number of volcanic earthquakes increased to 45 on Saturday, compared with zero the previous day.
On Sunday, the number of quakes detected had hit 21 as of 9 a.m. The agency warned of a possible eruption and volcanic cinders as fumarolic activity has been intensifying in areas around Owakudani, a volcanic valley in the Hakone area about 80 kilometers southwest of Tokyo.
After the alert level was raised, the town of Hakone decided to restrict entry around the crater and close a road leading to the area.
The operator of the Hakone Ropeway also suspended its services running through Owakudani on Sunday.
In 2015, small eruptions occurred at the 1,438-meter mountain and the agency's alert level was raised to 3, warning people not to approach a larger swath of area surrounding the volcano.
Prior to those small eruptions, geological evidence has suggested that the mountain last erupted between the late 12th and 13th centuries.