The second production unit of Peter Jackson's company, 3Foot7 Ltd, began setting up camp in a Cattle Flat Station paddock at the base of the Treble Cone ski area access road on Monday.
The film crew began arriving on Tuesday for a single day's filming, but visitors were kept out by security guards.
Unit manager Belinda Lee Hope apologised for having to decline to give any details about the unit's activities, but said she could understand if locals were excited about the film crew being in the area and that Wanaka locations could appear in the film.
She enthused about the scenery, the hot, calm weather and the friendliness of locals.
The crew was enjoying working and staying in Wanaka, she said.
"It is great. It is a perfect day. And all the local helicopter companies have been great," she said.
At least four Queenstown-based helicopters, 40 trucks and another 40 vehicles were at the camp. Ms Hope said the second production unit was normally much larger, but had split into two camps for a while.
When the Otago Daily Times visited, Mt Aspiring Rd was busy with traffic and helicopters were constantly on the move.
One helicopter ferried a large box into the mountains on a strop, another hovered over Twin Falls and two more were hovering over the peak of Treble Cone.
The second production unit of 3Foot7 is directed by Andy Serkis, but there was no confirmation he was in the Matukituki Valley.
Publicist Ceris Price also declined to reveal any information about who was around or what part of the story was being filmed but said she understood locals were curious.
"I am afraid they will have to wait until they see the film," she said.
"We have had amazing support from local people and they have all been very co-operative. We are very grateful for that. And it is a very beautiful area. We love filming in that country and showing it off," she said.
She also declined to say where the second production unit would go next.
Filming was expected to finish yesterday and the camp was expected to have moved on by tomorrow.
The Hobbit's star-studded cast includes Martin Freeman (Bilbo Baggins), Sir Ian McKellan (Gandalf) and Richard Armitage (Thorin Oakenshield).
Serkis will reprise the role of Gollum from Peter Jackson's The Lord of the Rings film trilogy.