Hackers stole $534 million from Japan’s digital currency exchange Coincheck, according to local media reports.
Coincheck's statement said, hackers broke in Friday at 02:57 (1757GMT).
The crypto-currency was sent from the NEM address of Coincheck.
NEM is a crypto-currency built on top of the blockchain like Bitcoin.
Japan's Kyodo News Agency reported that Coincheck President Koichiro Wada said during a press conference held late Friday that the company may seek financial assistance.
The Tokyo based company froze transactions for all crypto-currencies after the cyber attack except Bitcoin.
"Purchases and sales of cryptocurrencies other than BTC (altcoins) are currently restricted. Please accept our apologies for this inconvenience," Coincheck said on its webpage.
"We sincerely apologize for the inconvenience this has caused everyone. Please follow the official Coincheck blog and our official social media accounts for updates," it added.
After the theft, the total value of the crypto money exchange declined by nearly 10 percent, while there was a loss of six trillion Japanese yen ($55.3 billion).
This could be the biggest crypto-currency theft.