Immigration officials are trying to track down affiliates of an international passport fraud ring believed to be in New Zealand.
Indonesian police last week arrested four people in relation to the falsifying of visas and passports of numerous countries, including New Zealand.
One person was reportedly caught with 230 passport
covers, 93 completed passports and some immigration stamps.
But police said five associates had already left Indonesia for New Zealand.
The Department of Labour said its border staff were working with police to track up to five people believed to have arrived on false passports.
The department's deputy secretary, Mary Anne Thompson, said the sophistication of the fraud meant there was little to indicate they were not bona fide travellers.
"We regularly identify people with false passports and prevent them from entering New Zealand.
"What concerns us, along with many other countries, is the level of sophistication criminals are using in order to enter countries. It is an ongoing international challenge."
Ms Thompson understands that Australia, Canada and the United States were some of the other countries targeted by the ring.
"A staff member from New Zealand, the person that sparked this investigation, is in Indonesia helping the authorities with their inquiries," she said.
Given that the investigation was ongoing, she could not provide details of the operation.
A spokesman for Immigration Minister Paul Swain said the minister would be briefed this week.
New Zealand Police spokesman Jon Neilson has said four people were arrested in the operation.
"These arrests demonstrate the good working relationships of the department, the police, and Indonesian authorities," Ms Thompson said.
"We are pleased at the outcome of this investigation.
"The department invests heavily in detecting fraud, and preventing people who should not be in our country from entering."
The fraud is believed to be unrelated to the operations of the Immigration Service's Jakarta office.
Indonesia, the world's largest Islamic nation, is home base for the militant Jemaah Islamiyah, an al-Qaeda affiliate.
