One of Arthur's Pass' most iconic huts has been burnt to the ground.

A tramping group came across the smouldering remains of Casey Hut on Saturday afternoon.

The Department of Conservation (DOC) said the fire started sometime between Thursday and Friday last week.

The hut appeared to have collapsed in on itself and the fire did not spread to surrounding vegetation, despite the dry nor-west conditions.

Fire investigators and DOC staff assessed the hut remains on Monday morning. Initial results suggested the fire started around the hut entrance or woodstove.

DOC technical support officer Craig Alexander said it could cost up to $300,000 to replace the hut.

"There's all kinds of other things that need to be taking into account.

"Whenever we lose a hut, it's a huge investment to put one in there and to have one lost is a huge loss".

DOC senior ranger Pete Brady said the hut was in a popular area for weekend tramps and was used as a starting point for longer treks such as the route to Lake Minchin and Taramakau River.

"The six-bunk Trust Poulter Hut is a further one-and-a-half hours trek up the Poulter Valley; this could just put the option for a family overnight tramp just out of reach for some user groups".