Cryptocurrency mining marketplace NiceHash announced Wednesday that it suffered a security breach that resulted in a loss of as much as $62 million in Bitcoin.

The announcement came after hours of speculation sparked by the service being unavailable for the better part of Wednesday. Several reports from users noted that their Bitcoin wallets associated with NiceHash had been emptied.

While NiceHash originally claimed to be “under maintenance” during the outages, the company admitted that it had suffered a security breach involving the NiceHash website that resulted in loss of funds.

“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 , calling the breach “a matter of deep concern.” The company also apologized to its users for “any inconvenience” the breach may have caused.

While NiceHash has yet to place an amount on how much is stolen, a Bitcoin wallet address highlighted by NiceHash users that appeared Wednesday and has received a large deposit out of nowhere contains 4,736.42 BTC, valued at about $62 million at current prices.

The full extent of the breach is still unknown, and it is not clear if the attackers were able to compromise user information in addition to stealing Bitcoin. NiceHash has advised its users to change their passwords as a safety precaution.

In the meantime, the company is investigating the cause and breadth of the breach. It promised to provide regular updates to its users as the information became available. "We would not exist without our devoted buyers and miners all around the globe," the company said. "We ask for patience and understanding while we investigate the causes and find the appropriate solutions for the future of the service."

While some users of NiceHash have expressed disappointment online, others have said they would continue to use the platform for purposes of mining cryptocurrency—just not for storing it. Others were ready to abandon the platform entirely, frustrated by the breach and the fact that the company didn't have security levers that would prevent large withdrawals.

Others still began theorizing the breach may not have been a breach at all but rather an "inside job" carried out by the operators of NiceHash. One user posting on Reddit, identifying themselves as a penetration tester with familiarity of security breaches, claimed most cryptocurrency services keep the majority of funds in cold storage that cannot be accessed remotely.