NiceHash, touted as the one of the world's largest cryptocurrency mining marketplaces, said hackers had compromised its payment system and emptied its entire virtual Bitcoin wallet. The company said it was halting operations for 24 hours and was currently investigating the incident.
"Our payment system was compromised, and the contents of the NiceHash Bitcoin wallet have been stolen. We are working to verify the precise number of BTC taken," the company said in a statement on Wednesday (6 December).
"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."
The company did not specify how much Bitcoin was stolen in the breach. However, a BTC address shared by a NiceHash user on Reddit suggests that a sum of 4,736 BTC ($67m, £50m at current rates) was stolen, CoinDesk reported.
"We understand that you will have a lot of questions, and we ask for patience and understanding while we investigate the causes and find the appropriate solutions for the future of the service," the company said, advising users to change their online passwords as a precaution.
"We are truly sorry for any inconvenience that this may have caused and are committing every resource towards solving this issue as soon as possible."
The cryptocurrency mining service allows customers to offer up their extra computer processing power for the hefty maths calculations required to create or mine new Bitcoin or other digital currency. It also allows NiceHash users to purchase computer processing power from other users.
NiceHash users typically mine altcoins in exchange for their value in Bitcoin.
NiceHash initially sent out two tweets on Wednesday informing customers that its servers were down for "maintenance" and its team was working on a fix. However, the company later revealed that its servers had been compromised.
Its site still displays a security notice regarding the breach.
As cryptocurrency continues to grow exponentially in popularity and value, this isn't the first time hackers have targeted a digital currency platform. In July alone, Bithumb, CoinDash, Veritaseum and Parity Technologies suffered breaches resulting in the theft of tens of billions of dollars.