Signs of wallabies have been reported in Alexandra on the Otago Rail Trail, which the regional council says could mean the pest has spread right into the Maniototo.
Last year the Otago Regional Council called for a comprehensive strategy to stop wallabies from crossing the Canterbury border.
Wallabies cause damage to native forests, compete with cattle and sheep for pasture, and are capable of reaching very high population numbers.
Three pairs of wallaby were introduced to Waimate in South Canterbury 140 years ago; now there are estimated to be hundreds of thousands of them, spreading at about 50 square km a year.
As part of its response, the Canterbury Regional Council put a fence up to stop the animals hopping across the Aviemore Dam at night and getting over the Hawkdun Range into North Otago.
Otago Regional Council environmental managing director Scott MacLean said it was worrying to see the wallabies spreading further.
"The most recent report was some wallaby sign sighted by a landowner just outside of Alexandra. We've got to try and establish how they got there - if they got there naturally or were the result of an illegal release."
Mr MacLean said the Otago Regional Council was not pleased to see signs of wallabies on the Otago Rail Trail.
"It's certainly concerning that they're pressing into areas like that, at this stage there was only sign found and no animals - so we're going to concentrate some surveillance efforts in that area."
Asked when the council was going to spend serious money on the problem, Mr MacLean said they are still in the quantifying stage.
"As we've raised awareness we're getting more and more people engaged and informing us of potential wallaby sightings so at the moment it's quantifying the problem in order to make some appropriate budget setting."
There are a number of biosecurity staff out in various locations and contractors with wallaby dogs in the Hawkduns' Range, said Mr MacLean.