Thirty hikers are feared to have died near the peak of Mount Ontake, following a volcanic eruption on Saturday.

About 250 people were initially trapped on the slopes of the popular site, but most are thought to have made their way down.

The volcano, located approximately 125 miles west of Tokyo, erupted without warning on Saturday, spewing ash and rocks.

The eruption forced many of those on the mountain to make emergency descents through clouds of volcanic ash and falling rocks.

Japan’s meteorological agency raised the alert level for Mount Ontake to 3 on a scale of 1 to 5.

It urged people to stay away from the mountain, warning ash and other debris could fall up to 4 kilometers (2.5 miles) away.

Mount Ontake sits on the border of Nagano and Gifu prefectures. The volcano’s last major eruption was in 1979.