Bad weather and volcanic tremors hampered efforts Tuesday to look for survivors and recover bodies from Mount Ontake in central Japan.
An on-off rescue effort was halted again before 8 a.m. on Tuesday.
"Volcanic tremors have increased since early morning. The intensity is almost the same as that observed on Saturday night," said an official of the Meteorological Agency.
The official was speaking after a meeting to map out measures to deal with the eruption.
Twelve climbers were officially declared dead as of Monday, and the bodies of 24 others were still lying on volcano's slopes. The National Police Agency said at least 69 people sustained injuries.
The volcano, which straddles Nagano and Gifu prefectures, erupted before noon Saturday, a time when many hikers were out and enjoying the autumn climbing season.
The search involves about 850 police officers, firefighters and Self-Defense Forces troops, who were put on standby following the suspension of the search on Tuesday morning.
Operations ground to a halt on Sunday and Monday because of toxic gas spewing from the 3,067-meter volcano's vents.
Local police said rescuers will use a Ground Self-Defense Force helicopter to return to the ash-covered peak once conditions improve.
The meteorological agency maintained its eruption alert for Mt. Ontake at level three on a five-grade alert system, which restricts entry to the mountain and hills nearby.
The weather agency also warned that the volcano might throw rocks anywhere within a roughly 4-km range of the crater and that pyroclastic flows could occur.
Mount Ontake is especially popular with tourists in the fall. It last had a major eruption in 1979, when it expelled over 200,000 tons of ash.
It underwent a minor eruption in 1991, and in 2007 there were multiple volcanic earthquakes.
