The potential rat dropping on Whenua Hou/Codfish Island will undergo DNA testing to determine its origin.

A potential rat dropping found on an island that has been predator-free since 1998 - and is the home of the Kākāpō Recovery Programme - has sparked a "full-scale incursion response".

The Department of Conservation (DOC) leapt into action following the discovery on Whenua Hou/Codfish Island, off the west coast of Stewart Island.

A team equipped with tracking tunnels, camera monitoring gear and traps was deployed to the island on Thursday.

NEIL RATLEY/FAIRFAX Whenua Hou/Codfish Island is three kilometres off the west coast of Rakiura/Stewart Island and is only accessible by air. It has been predator free since 1998.

It comes after news Sirocco the celebrity Kākāpō hasn't been seen in over a year, and the death of another Kākāpō, Blake, earlier in December.

READ MORE:

* Sirocco the celebrity kākāpō remains AWOL

* 'Crusty butt' virus affecting Southland kākāpō

​* Saving the kākāpō on Codfish Island

* Rare kākāpō released at Little Barrier Island

* Seven things you probably didn't know about kākāpōo

The faeces, measuring about 2.8 centimetres in length, was found by a researcher studying South Georgian diving petrels on Sealers Bay beach and reported to DOC on Wednesday morning.

CAMERON BURNELL/FAIRFAX NZ Sirocco the Kakapo has not been sighted on his home, on a Fiordland island, since March 1, 2016.

It was suspected to be from a Norway rat, however, DNA analysis was required for confirmation.

DOC Murihiku operations manager and response leader Tony Preston says while it hadn't been definitively identified there was enough evidence to act.

"Whenua Hou is one of the most important sites for biodiversity recovery in New Zealand and any evidence of an incursion is treated very seriously. It only takes one pregnant rat to wreak havoc on a pristine ecosystem.

JOHN HAWKINS/Fairfax NZ Jo Leadington DOC Senior Ranger Kakapo talks about the recovery programme in Invercargill

"Because of this we're taking a better safe than sorry approach and doing everything we can to identify, isolate and exterminate any unwelcome arrival."

Dr Andrew Digby, a scientist for the Kākāpō and Takahē recovery programmes, said on Twitter: "No immediate threat to kakapo, but impacts could be far-reaching."

Kākāpō operations manager Deidre Vercoe said while a rat shouldn't pose any risk to an adult kākāpō, eggs and chicks would be vulnerable.

However, the critically endangered parrots were not expected to breed on Whenua Hou this summer, with the next breeding expected to be in early 2019.

Whenua Hou is located three km from the coast of Rakiura/Stewart Island. It has been predator free since 1998. As a nature reserve it has the highest protection available in New Zealand and entry is by permit only, with strict quarantine rules in place.