Bitcoin stolen in hack on NiceHash cryptocurrency mining marketplace

Hackers may have gotten away with $60 million worth of bitcoin after a cyber attack hit the cryptocurrency mining platform NiceHash.

Users highlighted the cyber breach on Reddit and Twitter Wednesday, with some saying they could lose hundreds of dollars.

NiceHash lets people offer computing capacity for bitcoin miners to mine digital currencies. Cryptocurrency miners work out complex mathematical equations to add cryptocurrency transactions to decentralized public ledgers called blockchains.

The mining marketplace initially said its service was undergoing "maintenance"on Twitter, later adding it was "working hard" to resolve issues affecting the site.

NiceHash said in a statement it was "investigating the nature of the incident," and that it would close down its site for a day.

"We are working to verify the precise number of BTC (bitcoin) taken," the company said. "Clearly, this is a matter of deep concern and we are working hard to rectify the matter in the coming days.In addition to undertaking our own investigation, the incident has been reported to the relevant authorities and law enforcement and we are co-operating with them as a matter of urgency."

While NiceHash was unable to specify how much bitcoin had been stolen, users have pointed to a bitcoin wallet which holds 4,736.42 bitcoins — equivalent to $68 million.

Andrej P. Škraba, head of marketing at the firm, confirmed to news agency Reuters that around 4,700 bitcoins — worth roughly $68 million at current prices — were lost in the hack.

CNBC reached out to NiceHash Chief Executive Marko Kobal for comment but he was not available at the time of publication.

This wouldn't be the first time people have lost millions in cryptocurrency. In November, millions of dollars worth of Ethereum were "accidentally" frozen on the cryptocurrency wallet provider Parity after a user "suicided" the wallet, deleting its code and freezing all ether tokens contained within.