Customs are investigating Hamilton company Pacific Aerospace for allegedly exporting parts to North Korea.
A New Zealand-made aircraft from Pacific Aerospace turned up at a North Korean military airshow painted up in the hermit state's colours in September last year.
The plane was photographed at North Korea's first ever public airshow, which featured fighter jets and military helicopters. The Hamilton-made PAC P-750 XSTOL, which has a North Korean flag on its tail, is used for skydiving and could be used by paratroopers.
Pacific Aerospace chief executive Damian Camp said at the time he was looking for answers.
"We're trying to get some detail on that because that aircraft is owned and operated by a Chinese company."
He said his company had sold the 10-seater plane to the Chinese company, translated as Free Sky, several months ago.
"I'm interested to find out more detail on it - we're going to find out what the detail is there. It's certainly nothing to do with us we've got no involvement with it. We're well aware of the restrictions into that part of the world - we're not interested in cutting across any of those," he said in September.
A UN Security Council report, however, showed a chain of emails that suggest the company knew its plane was in North Korea and it had been contacted by the Chinese company for parts and training.
The Chinese counterpart emailed Pacific Airspace regarding parts and saying that North Korean operators should be "trained ASAP for this aircraft operating".
Pacific Aerospace replied that they would co-ordinate training in China.
"[Name redacted] departs for China tomorrow and will co-ordinate with you to deliver the training in how to replace the flat motor," the email read.
There are strict United Nations sanctions banning a wide range of exports and services to North Korea in response to its nuclear weapons programme.
Pacific Aerospace said they had no comment at this time.