A New Zealand firm could face terrorism charges or prosecution for violating United Nations sanctions on North Korean weapons trading.

SP Trading, which is registered to an office in Auckland's Salvation Army building in Queen St, chartered the Georgia-registered Illyushin 76 cargo plane seized in Bangkok as it was flying from North Korea to an unknown third country. It carried missiles, explosives and assorted weapons.

The shell – or non-trading – company that owns SP owns another firm that last month bought $70 million worth of Azerbaijan oil destined for an unknown country.

A spokesman for Foreign Minister Murray McCully said of SP Trading that he was "aware of the alleged link and we are trying to find out much more as we can urgently".

Police confirmed they were involved and said that "when more information is obtained we will determine where the investigation will go".

Sources close to the investigation said charges could be laid under the 2002 Terrorism Suppression Act, which makes it a criminal offence to take part in, finance or recruit for a terrorist organisation or terrorist act.

United Nations sanctions banning North Korea from exporting any arms except light weapons were implemented in June after Pyongyang tested a nuclear warhead.

Thai investigators are unsure where the plane, operated by Georgia's Air West Ltd, was heading or who co-ordinated the flight plan.

Air West director Nodar Kakabadze told the Wall Street Journal that the company had no information on SP Trading.

"We signed a contract with SP Trading November 4 this year to carry out some flights. That's it," he said.

"I know nothing more about the company, and we'd never worked with them before."

The five-member aircrew have denied knowledge of weapons onboard.

They have been charged with illegally possessing heavy weapons and mis-stating details of the cargo.

SP Trading was registered on July 22 this year with offices at Level 5, 369 Queen St.

Part of the floor is operated by Danite Corporate who say they rent "virtual offices" – address services that allow users to reduce office costs – to dozens of companies.

A woman referred inquiries to its registered director, Lu Zhang, also known as "Lulu", and Paul Taylor.

A man who would say only that his name was Paul said the pair were "not here".

SP Trading is owned by Vicam (Auckland) Ltd, of the same address. Its director is Nesita Manceau, a New Zealander living in Vanuatu, which is a tax haven.

Vicam's shares are 100 per cent owned by GT Group of Vanuatu.

GT director, New Zealander Ian Taylor, said he would not comment on SP Trading.

"As you can imagine I have had a few phone calls and to be honest, while I am of course aware of it, I basically handle marketing for GT group, so the details of the company I have absolutely no knowledge of and therefore I cannot make any comment."

Vicam owns Sumato Energy Group, also at 369 Queen St, whose listed director is Mr Taylor. The company registration was lodged by Ms Manceau.

Last month the State Oil Company of Azerbaijan announced a ballot for one million barrels of Azeri light crude had been won by Sumato.

It was shipping it to an unnamed third country.