Coincheck Inc., a Japanese cryptocurrency exchange that was hacked on Friday, resulting in the loss of around $400 million in NEM tokens, has promised to refund all of its affected customers.

The response to what could be the largest cryptocurrency hack in history was surprisingly strong. Details of the hack were first revealed at a media conference Friday, with exchange President Wakata Koichi Yoshihiro and Chief Operating Officer Yusuke Otsuka saying that about 500 million NEM tokens had been stolen, at the time worth approximately $533 million.

The company didn’t share how the tokens were stolen. It said only that it had been sent “illicitly” outside the exchange and that it suspended all cryptocurrency trading except on bitcoin until the safety of all client assets could be assured.

Coincheck announced Sunday morning local time that it intended to repay all 260,000 users impacted by the theft of NEM tokens, at a rate of 88.549 yen (82 cents) for each coin and that the final number of tokens stolen came to 523 million. How the company intends to fund the refunds was not made clear.

“The timing of the reimbursement and the application process are currently under consideration,” the company said. “The source of the refunded money is being carried out using our own capital.”

Coincheck is likely to gain particular attention from Japanese authorities. Bloomberg reported that the compay had been trading for four months past its deadline for receiving a license necessary to operate. The report also noted that the Japanese Financial Services Agency is getting ready to penalize Coincheck in relation to the hack.

Japan legalized bitcoin and other cryptocurrencies in April. As part of that recognition, it also moved to regulate cryptocurrency exchanges, with the first exchanges obtaining registration in October. Those regulations, introduced in response to the alleged hack of Mt. Gox in 2014 — until now the largest on record — included requirements such as building a strong computer system, segregating customer accounts and checking the identity of customers.

Image: Coincheck