Three very large transactions worth about NZ$5.8 million were made out of Kiwi cryptocurrency exchange Cryptopia's wallets in the early hours of the day it suffered a security breach.
However, the Christchurch-based company refused to confirm exactly how much was stolen.
An exchange is a website where cryptocurrency traders buy, sell and often store currencies like Bitcoin, Ethereum, Ripple and many others, and a wallet is a unique address which owns a certain amount of currency.
Cryptopia last night confirmed on its Twitter account about 9pm that it had suffered "a security breach which resulted in significant losses" on Monday, January 14.
"Once identified by staff, the exchange was put into maintenance while we assessed damages," they said.
"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.
"Until this has been carried out, the Cryptopia Exchange will remain in maintenance mode, with trading suspended."
According to cryptocurrency transaction tracking site Etherscan, three very large sums of cryptocurrency were transferred out of two wallets known to be linked to Cryptopia in the early hours of January 14.
The first was a transfer about 2.30am NZT of about US$2.43m (NZ$3.56m) worth Ethereum from a first Cryptopia wallet to an unknown wallet.
The second was a transfer about 2.35am of about US$1.18m (NZ$1.73m) worth of Centrality (CENNZ), which came out of another of Cryptopia's wallets and went to a second unknown wallet.
A third transfer took place about 2.40am, and about US$371,000 (NZ$543,000) worth of DAPS was transferred from the second Cryptopia wallet to the second unknown wallet.
The DAPS organisation this morning said in a statement that "we have reached out to all the exchanges we are listed on to freeze deposits from this suspected hacker wallet," citing the wallet address into which the CENNZ and DAPS transfers were made.
Centrality has not commented.
Cryptopia refused to answer questions about the suspect transfers or the amount taken, saying only that "we cannot comment as this matter is now in the hands of the appropriate authorities".
Police have said in a statement that "a significant value of crypto-currency may be involved and Police are taking this very seriously.
"A dedicated investigation team is being established in Christchurch including specialist police staff with expertise in this area."