Family members warned former senior public servant Sharon Armstrong not to go overseas to meet a mystery man.

But Ms Armstrong, the former deputy chief executive of the Maori Language Commission, ignored their concerns and flew to Argentina last week to pick up something for the man she'd met on an internet site.

Before she could meet him in London she was arrested on April 13, her birthday, at Buenos Aires airport with 5kg of cocaine in a suitcase.

The Class A drug has a street value in New Zealand of up to $2 million. Interpol is now hunting the man, who has disappeared.

Kapoi Mathieson said her cousin went to Buenos Aires to pick up a bag for a man she'd met online and was then meant to meet him in London.

"She was going to fly directly to London from Australia and then he called her and needed her to pick something up for him in Argentina. So he paid for the change in the ticket and she went via Argentina, picked up whatever it was, and then was detained at the airport."

Before she left family warned her the trip sounded "dodgy".

"From what I've heard she's met this man online, they've been dating for several months," Ms Mathieson said.

"They were going to meet, this was their first meeting, and everyone - all the family - all said to her 'don't do it, don't do it, it sounds a little bit dodgy' but she was more of the mind of 'can't you guys be happy for me'."

Ms Mathieson said her behaviour was completely out of character.

The first her family knew something was wrong was when her regular email updates suddenly stopped.

"She texted her daughter 'I'm at the airport' and then, "I'm in Buenos Aires'."

But for 24 hours she heard nothing so phoned an aunt in Australia.

She was sure her cousin was the victim of an "affair of the heart" and being taken advantage of rather than any sinister motives.

"All of my family are gobsmacked - we can't believe it. We truly believe there is no way on earth that she could be a drug mule for someone."

Since her arrest, Interpol had been in contact wanting to know anything about the man who had vanished.

Ms Mathieson said her cousin's ordeal was a "great warning for other single females" who met men overseas off internet sites.

The Herald understands Ms Armstrong's family were worried enough about her that they called the New Zealand Embassy in Buenos Aires to tell them they thought she could be in trouble.

Ms Armstrong had been working as a contractor for Wellington-based Maori education and language company Haemata since February.

A Foreign Affairs and Trade Ministry spokeswoman said embassy staff were providing assistance.

New Zealand does not have a prisoner exchange programme with Argentina. The charge carries a maximum penalty of 15 years jail.

- Additional reporting: Anna Leask