TOKYO — Seven teenagers from a high school mountaineering club and a teacher died in an avalanche on Monday in an area of northeastern Japan that had been blanketed by unusually heavy spring snows, the authorities said.

The students and the teacher were training about 100 miles north of Tokyo, in an area where the weather bureau had issued an avalanche warning urging caution a day earlier. Dozens of other students and teachers were injured.

“Suddenly everything turned white,” a male student who was caught in the cascade of snow said in a telephone interview with NHK, the Japanese national broadcaster.

“The teacher at the front yelled, ‘Get down,’ so we dropped down and got covered in snow,” said the student, who was not identified by name. “Then those of us who could move helped dig out people who were buried.”

About 60 students from seven high schools in rural Tochigi Prefecture were participating in the annual early-spring climb. The area has been in the grip of snowstorms strong enough that rescue helicopters initially had trouble reaching the avalanche zone, according to Japanese news reports.

The authorities in Tochigi initially said they believed all eight victims were students. On Tuesday, after positively identifying the dead and notifying their families, they released their identities to the Japanese news media. One was identified as a 29-year-old teacher; the other seven were teenagers aged 16 and 17.

Television news footage showed rows of ambulances and other emergency vehicles waiting in the still-falling snow as crews worked to find and rescue survivors. Prime Minister Shinzo Abe spoke of the disaster in Parliament, saying officials were “making every effort to respond.”

After several hours, rescuers began bringing down bodies covered in blue plastic tarps.

The students were from Otawara High School, which has one of the top school mountaineering clubs in this mountain-filled nation, having won the Tochigi prefectural title for competitive climbing eight years running, according to its website. Survivors said members of the Otawara club were leading several groups of students during a trekking exercise on a low-altitude slope when the avalanche struck.

About 40 participants suffered injuries, all but two of them minor, the authorities said.

The students and their teachers may have thought they were playing it safe.

Officials from the Tochigi board of education said at a news conference that the group of seven schools had originally planned to climb to the top of Mount Chausu, a 6,300-foot peak, to cap a three-day training program that began on Saturday.

The group had been camping at a ski resort near the mountain’s base, the officials said, learning lessons on how to climb in the snow, including how to avoid avalanches.

But conditions worsened starting Sunday night, with a storm that brought high winds and a foot or more of new snow, according to the Tochigi branch of the Japanese national weather service. Warmer temperatures during the day on Monday made the accumulation especially unstable, the weather service said.

So instead of climbing the mountain as planned, the board of education said, teachers decided to have the students practice trekking on the much lower — and presumably safer — slopes around the ski resort.

Given the daunting conditions, even that was too much for some students. Prefectural officials said about a dozen students stayed behind because they lacked the confidence or the equipment to move through the deep snow.

“I heard yelling. Then afterward I heard the sound of sirens and helicopters,” one student told NHK.

He said he was in a tent about 300 feet away from the avalanche when it occurred, around 9:20 a.m. “I couldn’t contact some of my friends for a few hours,” he said. “I learned how scary a mountain can be.”