An Australian woman and her family who went missing at a popular Japanese ski field survived a freezing night in the wild after building a cave to shelter from treacherous conditions.
The 57-year-old woman and her three sons aged between 18 and 25 were reported missing near Nozawa Onsen in heavy snow conditions after they raised the alarm on Facebook on Monday afternoon.
Police indicated one of the group used Facebook to contact a person outside Japan, who then raised the alarm. "I'm skiing and I got lost," the message said, according to the Mainichi newspaper.
The search resumed on Tuesday morning and the family, whose names have not been released, was found by ski patrol members around 8.45am local time.
Japanese TV broadcast images of the woman and her sons being led to safety. They were wrapped in blankets and accompanied by police and other rescuers who walked them to waiting ambulances, the All-Nippon News Network footage shows.
They were reported to be well but were taken to hospital for health checks.
Police told AAP the group had since been released from hospital. A police spokesman said the woman, a doctor, had been out with her three sons, an engineer aged 25, an office worker aged 23, and a student aged 18.
Daisuke Tozawa, who works at the Nozawa Onsen Snow Resort, said he understood the group had been skiing in the back country over Kenashi mountain, which is outside the official ski routes, when they encountered trouble.
"In the last couple of days there was a lot of snow and yesterday was snowing as well," Mr Tozawa said.
"It is dangerous. There was a high risk of avalanche yesterday."
Nozawa Holidays said the family "would have faced a freezing night on the hill", with 25cm of snow falling overnight - the seventh day in a row of heavy falls.
"Apparently they dug a snow cave which would have almost certainly saved their life," the company said in a Facebook message to other holidaymakers. It said such caves could provide warmth and shelter.
"Do not go into the backcountry if you don't know what you're doing. Do not duck ropes."
Jennifer Johnston, another Australian tourist who has been staying at Nozawa Onsen since Thursday, said the decision to build a snow cave was "possibly the smartest thing they could have done" in the situation.
Ms Johnston said conditions had been "very challenging" on the ski fields.
"One of the ladies who's staying in our lodge has just been out on what you could call an easy run and she just said the powder is phenomenal. It's a green run, but the powder is up to your knees in sections. Visibility is low as well," Ms Johnston told AAP.
"We had another Australian family arrive from Sydney yesterday afternoon and they just can't believe the cover. Conditions are what you'd call very challenging up top, visually. It's just the very mad keen ones who will go up."
Nozawa Onsen, in Nagano prefecture, northwest of Tokyo, is a popular destination for overseas skiers and snowboarders.
The incident follows warnings about the heavy snow conditions in the region.
People should not "head off-piste as there are some extremely unstable layers and the likelihood of becoming stuck is an almost certainty," the Nozawa Onsen Guide website said.
