The Department of Conservation believes people have illegally dug holes at a historically significant pā.
Staff found four unusual spade holes near the entrance of Pukerangiora Pā - situated near the Waitara River in Taranaki - prior to the current Covid-19 outbreak.
DoC believes they were dug by people using metal detectors to fossick for colonial items due to the site's history.
The pā was the site of multiple battles during the Musket Wars of the early 1800s, and was twice besieged by colonial forces during the New Zealand Wars.
The site falls under the rohe of the Pukerangiora hapū.
Chair Anaru White said the pā is historically important and needs to be protected.
"The Pā is a wāhi tapū and as kaitiaki we have the responsibility to ensure appropriate tikanga is followed at the Pā due to the significance of this site for the hapū and iwi," White said.
"This site is important in our history and we all need to help protect it."
DoC senior ranger Dave Rogers says it's likely the people who dug the holes were looking for artifacts like musket balls or military buttons.
"There is clear evidence at Pukerangiora Pā of someone having gone in and dug holes - we are assuming metal detectorists which is an illegal activity.
"We have received reports of people with metal detectors at Pukerangiora Pā in the past. DoC wants to remind visitors it is an offence under the Conservation Act as well as Heritage New Zealand / Pouhere Taonga Act to dig up a historic archaeological site and people can face prosecution and a fine if caught doing so."