UPDATED 4am Wednesday

An Australian mother and her three sons feared missing at popular Japanese ski field Nozawa Onsen following heavy snowfall have been found alive and well.

A decision to build themselves a snow cave to shelter from the freezing conditions for the night stop a mountain may have saved their lives.

Nozawa Holidays, the ski resort west of Tokyo where the family is staying, posted on Twitter on Tuesday morning that they had been “found and are all well”, having been located towards the bottom of Mt Kenashi.

“Great news and a strong message to everyone to take care in the mountains.”

The company later updated their statement to say the family had some minor frostbite.

“There has been an amazing amount of snow fall here in Nozawa Onsen over the last few days and the lure of the powder snow is great but it is not a time to be venturing outside of the resort area. Please stay on the dedicated runs and stay safe” the company said.

A search had recommenced on Tuesday after the Australian mother in her 50s and her three sons, believed to be in their 20s, did not return on Monday.

Japanese news website Mainichi reported that the woman and her sons contacted a Facebook friend to say: “I’m skiing and I got lost.”

Mt Kenashi, the peak of Nozawa Onsen Ski Resort. Photo: Nozawa Holidays

A spokesperson for the Department of Foreign Affairs had told AAP Australian officials were in contact with Japanese authorities.

Police believed they were missing somewhere near the summit, where the temperature was -11 degrees.

A local weather report on Sunday said the snow was deeper than head-high in parts, after a severe blizzard.

“Don’t head off-piste as there are some extremely unstable layers and the likelihood of becoming stuck is an almost certainty,” the report on the Nozawa Onsen Guide website said.

“There are clueless people out there … don’t be one of those people.”

The Nozawa Onsen hot spring resort is known as the birthplace of skiing in Japan.

– with AAP