Toxic gases and ash were still coming from the Mount Ontake volcano Monday, halting the search for more victims and the recovery of the bodies. Here's a summary of events and a guide to understanding them:

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SEARCH AND RECOVERY

So far, 12 bodies of victims killed in Saturday's eruption have been recovered, and 24 are still on the mountain. Several hundred emergency workers and soldiers are involved in the effort to remove the bodies and search for any others.

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A MOUNTAINTOP SHRINE

Ontake Shrine at the summit sits atop a stone platform overlooking verdant hills. The shrine, a lodge below it and nearby rocks are covered in ash up to 50 centimeters (20 inches) deep. The victims were found in or near the shrine and the lodge.

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HOW THE VICTIMS DIED

Authorities are focusing on three possible causes: injuries from rocks ejected from the volcano, toxic gases, suffocation from lung-choking ash — or some combination of them. At least some of the bodies had severe bruises, a Nagano prefecture police official said, speaking on condition of anonymity because he was not authorized to speak to the media.

Two experts said rocks flying out of the craters could be the main cause, because of the way the deaths are concentrated in one area near the summit. One survivor who protected her head with a knapsack told a Japanese broadcaster that she found a thermos inside flattened afterward.

Hikers might also have been incapacitated, either by flying rocks or toxic gases, and suffocated under a reported ashfall of up to 50 centimeters (20 inches). Hydrogen sulfide and sulfur dioxide can cause serious damage to the respiratory system, said Koji Ono, an official in the Japan Meteorological Agency's volcanic section.

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VOLCANO'S STATUS

The current alert status is Level 3, meaning people should pay attention to volcanic activity and should not approach the volcano. The scale ranges from Level 1, meaning emissions generally are contained within the crater, to Level 5, which is a warning to evacuate.

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Online: Japan Meteorological Agency (in English): http://www.jma.go.jp/en/volcano/