A rodent has been killed on Tiritiri Matangi Island, a bird sanctuary about 30km north-east of Auckland's CBD (file photo).

A rat that sparked a panic on a pest-free island in Auckland's Hauraki Gulf has been trapped and killed.

A routine check of tracking tunnels on the island, in Auckland's Hauraki Gulf, revealed rat footprints on January 8.

The footprints were found on two of the monitoring cards inside the tunnels, showing a rat had been through them sometime in the period between New Year's Eve and January 7, a statement from the Department of Conservation (DOC) said.

ROSE REES-OWEN/STUFF Sea birds such as dotterels and oystercatchers nest at Hobbs Beach on Tiritiri Matangi.

On Friday, DOC confirmed the rat had been caught in a trap and killed instantly. Its body was found at 6am.

READ MORE: DOC team scrambles to Tiritiri Matangi Island in search for rat

The dead rat would be sent to Auckland for scientific analysis.

"We're thrilled to have caught this rat as it posed a serious threat to the native birds and other native wildlife on Tiritiri Matangi," DOC's acting Auckland inner islands operations manager John Galilee said.

DOC ranger Polly Hall with the dead rat.

Tiritiri Matangi, about 30km north-east of Auckland's CBD, has been free of rats and other animal pests since 1993.

It is home to a number of native birds including takahē, kiwi pukupuku/little spotted kiwi and kōkako.

There are also tuatara, wētāpunga and five types of native lizard on the island.

Following the discovery of the rat footprints, two pest-detection dogs, Pai and Indie, were deployed to the island with their handlers to sniff out the rodent.

More than 50 additional traps and at least 60 extra tracking tunnels were also put in place.

Galilee said there was an "ever-present" risk of a rodent making it to Tiritiri Matangi.

"We want to remind boat owners to make sure there isn't a rat or a mouse stowed away on their vessel, whenever they're heading out to sea in the Hauraki Gulf."