Three people were found lying unconscious near a crater of Mount Fuji on Wednesday and were later confirmed dead, according to the police department of Shizuoka Prefecture.
They were found during the search for a 53-year-old male corporate worker from Hino, Tokyo, who went missing after going climbing on the mountain on Friday. The three people were found lying unconscious apart from one another near the crater.
The local police are working to confirm their identities.
Authorities have long warned climbers to take care when attempting to scale Japan's highest mountain, where hiking trails officially open on Monday.
Mount Fuji is covered in snow most of the year, but during the July-September hiking season, more than 220,000 visitors trudge up its steep, rocky slopes.
Many climb through the night to see the sunrise, and some attempt to reach the 3,776-meter summit without breaks, becoming sick or injured as a result.
Regional officials have raised safety and environmental concerns linked to overcrowding on the mountain, a symbol of Japan and a once-peaceful pilgrimage site.
Hikers using the most popular route to climb Mount Fuji — the Yoshida trail — this summer will be charged ¥2,000 ($13) each, with entries capped at 4,000 to ease congestion for the first time.