Mt. Gox said Friday it found 200,000 "forgotten" bitcoins on March 7, a week after the Tokyo-based digital currency exchange filed for bankruptcy protection and announced it had lost nearly all of the 850,000 bitcoins it held, worth some ¥51 billion at today's prices.

Mt. Gox made the announcement on its website. Online sleuths had noticed around 200,000 bitcoins moving through the crypto-currency exchange after the bankruptcy filing.

The exchange, headed by 28-year-old Frenchman Mark Karpeles, said the bitcoins were found in an old-format online wallet that it had thought no longer held any bitcoins, but which it checked again after the bankruptcy filing.