Eight Japanese schoolchildren are feared dead after an avalanche struck Tochigi prefecture on Monday, Japan’s Kyodo news agency reported. Around 50 people, including students and teachers from several schools, were believed to be at the site near the Nasu Onsen Family Ski Resort when the avalanche hit.

The children were showing no vital signs. At least 30 others were injured, while three are missing. The avalanche took place around 9.20 am in Nasu, 120 km north of Tokyo.

The students were participating in a mountain climbing event when the avalanche struck. The Tochigi government said two students and an instructor are missing, while three students were injured, The Telegraph reported.

Bad weather is hindering rescue operations, and helicopters have beem unable to reach the site. There has been more than 30 cm of snowfall in the area since Sunday, but the risk of an avalanche was heightened by the recent warm weather.