Mount Ontake, Japan (CNN) -- At least 31 people are presumed dead after rescuers found them showing no signs of life Sunday near the summit of a Japanese volcano that started erupting a day earlier.
Police said the people were in a state of "cardiac arrest," meaning that they were discovered without a pulse and weren't breathing but hadn't been declared dead by a doctor.
A coroner confirmed the first four deaths Sunday.
Rescue teams had begun searching Sunday for dozens of climbers who were caught by the sudden eruption of Mount Ontake.