Members of a search party looking for friends Jessica O'Connor and Dion Reynolds in the Kahurangi National Park made the discovery in the past few days.
The pair have not been seen or heard from since Saturday, May 9.
A photo of the jersey was reportedly sent to at least one local venue - the Roots Bar Tākaka, where Reynolds used to work as a chef - asking whether staff may recognise it as belonging to the 23-year-old.
However, it is understood no one could identify it and police have also ruled out a connection to the pair.
"At this stage, police believe it is unlikely to have belonged to one of the trampers," a spokeswoman said.
A Royal NZ Air Force NH90 helicopter has also been helping search efforts over the past few days.
A search for the pair resumed at first light this morning, police said.
Sergeant Malcolm York said the Defence Force was flying six teams into the area.
Today's search will continue to be centred around the Anatori River and the coastline, he said.
"Aerial searching will continue with support from a commercial and an NZDF helicopter.
"Five specialist tracking experts have been brought in from around New Zealand, as well as three search dog teams."
York said those heading into the bush are also expected to stay in overnight.
"More than 30 police staff and volunteers [are] working on the search operation from a number of different locations."
Heavy rain in the region had made searching unsafe in the past few days.
It has now been two and a half weeks since the friends, both aged 23, headed into the Kahurangi National Park to go tramping.
They had been due to return about five days later on Thursday, May 14.
LandSAR (search and rescue) NZ chief executive Carl McOnie said its team of volunteers were very skilled and were still holding onto hope.
"We want a result. We want to give families a result."
McOnie said they continued to get offers of help from all over the country, including from professional search and rescue volunteers in Auckland and Invercargill.
Although the trampers had been missing for some time now, he acknowledged that anything could happen.
"You never lose hope and you always have hope."
- Can you help? Anyone who has seen or heard from either Jessica O'Connor or Dion Reynolds since May 9 is urged to call Police immediately on 105 or 111
