Japan's Meteorological Agency is warning of a possible volcanic eruption at the hot spring resort of Hakone, near Tokyo.
The agency raised its alert level to two on a scale of five early on Sunday after the number of volcanic earthquakes increased at Mount Hakone the previous day.
It is warning that large volcanic rocks could fall around the crater at a valley called Owakudani.
It's the first time in four years that the alert level was set at two.
Hakone Town has decided to restrict travel near the crater.