More than 20 bodies remained near the summit of Japan's Mount Ontake as new tremors and venting gases forced search teams to abandon their efforts early Tuesday local time. Officials don't yet know precisely how many climbers were trapped when the volcano erupted Saturday, a busy day for hiking.

From Tokyo, John Matthews reports for NPR:

"Weather officials say they've detected new seismic activity around Mount Ontake, which could trigger another eruption at any moment. Police called off search efforts at 7 a.m. Tuesday local time, citing heavy concentrations of toxic volcanic gas and threat of further eruption."Even national guard helicopters, which would usually still fly after other rescuers retreated on foot, are now being grounded."Authorities are continuing to warn local residents of falling debris and fast-moving gas clouds in a 2 1/2-mile radius of the several newly formed craters. Some 800 rescuers await a decision on whether to resume again tomorrow, although the chance of finding survivors is already slim."

The Associated Press notes that "rescuers found five more bodies on Monday, bringing the death toll to 36. They have managed to airlift only 12 bodies off the mountain since the start of the eruption on Saturday because of dangerous conditions."

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