The bodies of 31 climbers have been found near the summit of Mount Ontake in central Japan, after the volcano erupted with tons of ash and poison gas on Saturday.  The blast came as a surprise, as Seismic sensors on the mountain didn’t detect any pressure building or lava flow underneath the surface prior to the eruption.

Rescue efforts will resume on Monday.  The Japan Self Defense Force dispatched helicopters to Ontakesan to rescue as many people as possible who had ducked into mountain lodges for shelter as the ash came down, but the search was temporarily called off because of toxic volcanic gases in the area.  At least 40 people suffered various injuries on both faces of the mountain, and scores made it down the slopes on Friday.

Officially, four people are dead.  Japanese officials often don’t update the death toll until after a medical examiner takes a look at the bodies. 

Mount Ontake straddles Nagano and Gifu prefectures in the Japan Alps about 210 kilometers west of Tokyo.  It’s generally pleasant climb, and popular with weekend trekkers.  250 climbers were on the mountain when it erupted, and some recorded video of the ash coming down on them.

“There were no earthquakes or strange smells on the mountain when I was there,” said 52-year old Satoshi Saito, who descended from Ontakesan an hour before the eruption.  “But a man who runs a hotel near the mountain told me that the number of small earthquakes had risen these past two months, and everyone thought it was weird.”