OTAKI, Japan - Firefighters, police and troops resumed search operations on a volcano in central Japan Monday after four confirmed fatalities with at least 27 other people feared dead.
More than 500 rescuers returned to Mount Ontake after the search had been called off on Sunday afternoon due to dangerous levels of poisonous gas.
"It depends on the (volcanic) situation how far they can go," a crisis-management official at the Nagano prefectural government said.
Smoke was still rising from the peak early Monday, but helicopters had begun an aerial search of the volcano, which is popular with hikers.
At least 31 people were found lying near the summit of 3,067-metre (10,121-foot) volcano, which erupted Saturday without warning, spewing ash, rocks and steam.
Four of the 31 were brought down and later confirmed dead. They were all men, aged 23-61.
Rescue workers were trying to air lift the remaining 27 people still on the volcano and in "cardiac arrest", a term usually applied before doctors can certify death.
Firefighters have separately confirmed more than 30 people were injured by flying rocks and inhaling poisonous fumes.
The meteorological agency forecast further eruptions, warning that volcanic debris may settle within four kilometres (2.5 miles) of the peak.
A suffocating blanket of ash up to 20 centimetres (eight inches) deep covered a large area of the volcano, and had forced up to 150 to seek refuge in mountaintop shelters at one point.
The mountain is popular with hikers, particularly in late September when the turning of the autumn leaves makes for dramatic scenery.