New Zealand police are appealing to any Australians who might have been drugged and assaulted while staying at a backpackers' lodge in the far north of the country.

The owner of Mainstreet Lodge in Kaitaia faces 39 charges of stupefying, indecent assault and making and possessing intimate visual recordings.

Michael Harris, 56, is alleged to have assaulted 16 young men, aged between 18 and 25, over the past two-and-a-half years at the backpacker lodge in the popular Northland tourist area.

Police said all of the men whom Harris is accused of attacking were international tourists, but did not release the nationalities of the victims.

Detective Senior Sergeant Rhys Johnston said there could be more victims and appealed for them to come forward.

NZ police said they have not had any calls from Australians in relation to the case.

"Callers are concerned about whether something has happened to them and we want to be able to provide these potential victims with the right support as well as gather the evidence necessary," Detective Johnston said.

He said police particularly want to speak with anyone who stayed in the owner's residence of the Mainstreet Lodge during the past two-and-a-half years.

The lodge has hotel-motel and dormitory style accommodation, but police said some tourists also stayed in the residence.

The town of Kaitai bills itself as the gateway to the far north of New Zealand, an area including Ninety Mile Beach, towering sand dunes and Cape Reinga, the country’s northern-most tip.

"The local community welcomes and values the many tourists it gets in the far north," Detective Johnston said.

"I want to reassure tourists and our local residents that we have a person in custody and are carrying out a thorough investigation.

"These are very unusual allegations and we will not let them impact on the reputation of a region known for being a favourite destination for overseas visitors."

Detective Johnston says anyone with information or concerns about the case can contact Kaitaia police by emailing: operationsnap@police.govt.nz

He said victims were unlikely to know that something had happened to them, but may have suspicions.

"We will deal sensitively with them and offer all appropriate support required," he said.

Local media said Mainstreet Lodge remained open for business, with staff giving assurances to guests that they are safe.

Harris moved from Auckland to Kaitaia two-and-a-half years ago.

Some media are reporting he was involved in hostels in Australia.

YHA Limited has told the ABC it has no record of Michael Harris working in any of its 90 hostels.

But a spokeswoman said there were more than 400 other hostels operating in Australia.

Harris is in custody and is due to appear in court next week.

ABC/AFP