Caught near the summit of Mt Ontake.

For one group of hikers there was no choice but to seek shelter in a nearby mountain lodge, while the volcanic rock and debris rained down.

When it was over, the group ventured outside, the mountain blanketed by ash. A difficult descent lay ahead.

But they were among the lucky ones.

Hundreds of climbers were believed to be on Mt Ontake when it erupted. More than 30 are feared dead. The search for survivors continues.