The police investigation of a Christchurch cryptocurrency trading company continues after a "significant value" was transferred without authorisation.

Police were advised late yesterday of an issue involving potential unauthorised transaction activity at Cryptopia, based in Christchurch.

In a statement tonight, police said the investigation is focusing on both a forensic digital investigation and physical scene examination.

"We are dealing with a complex situation and we are unable to put a timeframe on how long the investigation may take," police said.

"While police are unable to go into details about specific steps being taken at this stage, we can say that our focus includes commencing both a forensic digital investigation of the company, and a physical scene examination at the building.

"We are also aware of speculation in the online community about what might have occurred. It is too early for us to draw any conclusions and police will keep an open mind on all possibilities while we gather the information we need."

Police are still not in a position to say how much cryptocurrency is involved.

Cryptopia posted on Twitter to alert users that on January 14 it had "suffered a security breach which resulted in significant losses".

"Once identified by staff, the exchange was put into maintenance while we assessed damages," it wrote.

"Staff then notified and involved the appropriate Government Agencies, including NZ Police and High Tech Crimes Unit who are jointly and actively investigating the matter as a major crime and they are assisting us with advice."

The company said that until this is carried out, the Cryptopia Exchange would remain in maintenance mode, with trading suspended.

Police acknowledged there had been a significant police presence at the company's Colombo St address in Christchurch.

"A large team, including Canterbury CIB and specialist staff from the police High Tech Crime Unit, have been assigned to the case," police said.

"We would also like to make clear that Cryptopia are co-operating fully with the investigation team and a media report that police 'stormed' the building today is entirely incorrect."

Anyone with information which could assist the investigation can contact police by email at [email protected]