Although she is a club member, Miss Willen (20), of Akron, Ohio, was not part of a club trip when she went missing in bad weather on the Gillespie Pass track in Mt Aspiring National Park on Saturday.
Police and LandSAR Wanaka volunteers have temporarily suspended the search for Miss Willen, known as ''Ally'', whose name was released yesterday afternoon.
In a statement responding to Otago Daily Times inquiries, Otago University Tramping Club vice president Jamie Gardner said the club ''would like to extend our deepest sympathies to the family and friends'' of Miss Willen, who had joined the tramping club at the start of the semester, but was on a private tramping trip at the weekend.
''We have no knowledge about the circumstances of the accident beyond what we have seen reported in the media. Our thoughts are with the student's tramping party, any club members who may have known her, and, of course, her next of kin.
''We would like to extend our thanks to the police and Land Search and Rescue for their efforts so far, and wish for the best outcome with their search.''
Miss Willen had been studying at Otago University for a short time on an International Studies Abroad programme and was tramping with two other female friends from the university - from whom she became separated - when she went missing.
An extensive two day search effort focused on the Young River, where items of clothing and her backpack were found in the river.
Sergeant Aaron Nicholson said the search had been suspended for a few days to allow river levels to recede.
''So that when we recommence on Friday or Saturday we have the very best chance of finding Ally for her family.''
Miss Willen's father and uncle are in Wanaka monitoring the search this week and had been greatly appreciative of the search effort to date and the time dedicated to it by the LandSAR volunteers, Sgt Nicholson said.
''They are clearly distraught by this sudden and unexpected loss and very anxious to find Ally. The father is asking for privacy for him and his family at this very trying time.''
The International Studies Abroad programme's US based health, safety and security director Robin Reliford did not respond to an ODT email.
A local representative of the company said the women who were tramping with Miss Willen - also believed to be American study abroad students - had declined to speak to media.
The ODT understands Miss Willen had recently spent time tramping in the Abel Tasman and Fiordland national parks, the Kepler Track and on Roys Peak near Wanaka.
Since 2002, there have been at least nine drownings in rivers within or just outside Mt Aspiring National Park, as a result of tramping, jet boating or fishing accidents.
