The resort is located a short distance from Tokyo
The avalanche hit the Nasu Onsen Family Ski Resort in Tochigi prefecture at around 9.20am local time (0.20 GMT) on Monday morning and six people have been found showing no vital signs, according to local media.
Two students and one teacher have been injured, according to emergency services.
Three people are still missing and an investigation is now underway.
Students from a number of high schools were in the area to compete in a climbing event which was due to finish around midday on Monday, according to Japanese news site The Mainichi.
Chief Cabinet Secretary Yuka Kan said: "We will continue to evaluate the damage information and work closely with the affected local governments, we will make disaster emergency measures with the highest priority to the life-saving and rescue of the victims."
More to follow…