Nagano state police said the bodies were found near Mount Ontake in central Japan, which erupted shortly before noon on Saturday, spewing large plumes of smoke high into the sky and blanketing the area in ash.
About 250 people were initially trapped on its slopes, but most had made their way down by Saturday night.
The victims have been described as not breathing and with stopped hearts, which is the customary way for Japanese authorities to describe a body until police doctors can examine it.
Four people were transported back down the mountain yesterday and confirmed dead
A Japanese military helicopter rescued three people from the spectacular volcanic eruption that left many more injured and stranded on a mountain.
The search for a total of 45 missing climbers was called off for the night yesterday evening.
Mount Ontake in central Japan erupted shortly before noon on Saturday, catching mountain climbers by surprise and by yesterday afternon had injured at least 34, including 12 seriously.
The tally was lower than had previously been reported but the Fire and Disaster Management Agency warned that the numbers could still change.
Nagano prefecture official Sohei Hanamura said the condition of the three people rescued by the helicopter was not known.
Many were injured were unable or unwilling to risk descending 10,062ft Mount Ontake on their own.
Rescue workers had struggled to reach the area on foot.
With a sound likened to thunder, the volcano erupted on a clear autumn day, spewing large white plumes high into the sky and blanketing the surrounding area in ash. Smaller eruptions continued overnight.
About 250 people were initially trapped on the slopes. Some were offered refuge in shelters set up in four nearby towns.
In a video posted on YouTube, shocked climbers can be seen fleeing from the peak as an expanding plume of ash emerges above and then engulfs them.
Many of those who made it down emerged with clothes and backpacks covered in ash and told reporters they had been engulfed in total darkness for several minutes.
As well as choking clouds of toxic ash that forced people to try to breathe through makeshift cloth masks and completely blinded them, stones flung out by the volcano rained down on the people trying to flee.
Mikio Oguro, an NHK journalist who was on the slope on an unrelated assignment, said he saw massive volumes of smoke coming out of the crater, blocking sunlight and reducing visibility to zero.
“Massive ash suddenly fell and the entire area was totally covered with ash,” he said.
He and his crew had to use headlamps to find a lodge. “My colleagues later told me that they thought they might die,” he said.
Aircraft headed to Tokyo’s Narita International Airport had been diverted to Kansai International Airport in western Japan as a precaution.
Japan sits on the seismically active Pacific rim which makes it prone to volcanoes and earthquakes but there have been no fatalities from volcanic eruptions since 1991, when 43 people died at Mount Unzen.
Japan’s meteorological agency raised the alert level for Mount Ontake to 3 on a scale of 1-5. It warned people to stay away, saying ash and other debris could fall up to 2.5 miles away.
Mount Ontake, about 130 miles west of Tokyo, sits on the border of Nagano and Gifu prefectures, on the main Japanese island of Honshu.