The investigation into last week's fatal high school mountaineering lesson in Tochigi Prefecture is likely to time because many people are still being treated for their injuries.
A school official said the organizers did not expect an avalanche to occur in the area where the students were receiving training.
Of the seven Otawara High School students and one teacher killed at the ski resort in Nasu one week ago, funerals were held Monday for Hidetomo Hagiwara, 16, and teacher Yusuke Ketsuka, 29.
"We promised to meet up in April, but I never imagined we would meet like this," said Koya Nakano, 16, who went to the same junior high school as Hagiwara.
Another male teacher, who led a group of 13 that included Ketsuka, is still being treated, forcing police to postpone questioning until he recovers. The local education board said the injured teacher is an experienced climber.
At a news conference Wednesday, Shuichi Inose, 50, who was in charge of the March 27 event, said the school was aware of areas where avalanches tend to occur and decided there would be no problem as long as these high-risk areas were avoided.
The training event has been held every March since 1963, and the prefectural education board said no accidents had occurred for over 10 years.
Police have found that the avalanche at the Nasuonsen Family Ski Resort barreled at least 160 meters down the mountain and overwhelmed the climbers, instantly killing eight and injuring 40 others.
They said they plan to question the survivors with care, taking into account the physical and mental impact of the accident.