An Australian woman and her three sons reported missing in Japan after failing to return from a day of skiing have been found, the resort says.

The woman in her 50s and her three sons, who are believed to be in their 20s, did not come back from their ski trip on Monday.

The family was found at the top of a mountain, the Nozawa Onsen ski resort wrote on Facebook.

"All members are fine," the post read.

Police earlier said they believed the family were missing somewhere near the summit of the mountain at an altitude of 1,600 metres.

They said their search was prompted by a call from a relative of the family, who saw a post on Facebook which called for help.

The Nozawa Onsen resort is a popular destination for Australians. ( Wikimedia )

The Facebook message said they had dug a cave in the snow to shelter from the cold, Japanese broadcaster NHK reported.

Rescuers at Nozawa Onsen, near the west coast of Japan's main island, resumed their search on Tuesday morning (local time).

Police said the heavy snow in the region meant they could not use helicopters during the search.

The Nozawa Onsen resort is a popular destination for Australian skiers and snowboarders because of the powder snow.

Over the past three days there has been about 1.5 metres of snowfall at the resort.

Overnight temperatures dropped as low as -10 degrees Celsius, with a wind chill factor bringing it down to -20C.

'There's a magical element to it'

ABC reporter Kumi Taguchi is holidaying at the ski resort, and attempted to describe the snowy scene.

People walk through snow covered streets at the Nozawa Onsen ski resort. ( ABC: Kumi Taguchi )

"To give you context about how deep it is, when you are walking in the village, you are literally mid ankle deep or knee-deep in snow," Taguchi said.

"I had a ski lesson a couple of days ago. The guy who was teaching me — who is extremely skilful — he was saying that to manage in that powder snow higher up on the slopes … you have to have a lot of skill to get yourself out of it. Nearly 1.5 metres of snow has fallen in the last three days at the resort. ( ABC: Kumi Taguchi )

"There is no density to it. Once you are trying to push yourself out of the hole, you are literally pushing down into air.

"There's a magical element to it. When you are down lower, you are like 'this is beautiful'. It is light, you sink down into it

"Obviously in a place like this, people are coming and going, lots of groups, families, tourists, locals so how do you know who has gone up the mountain and how do you know who has come down?"