Mt. Gox says that it has found around 200,000 bitcoins - worth in the region of $116 million - in an old digital wallet.
The Japan-based exchange filed for bankruptcy protection last month after claiming to have lost 850,000 bitcoins, around seven per cent of all the coins in circulation.
However, in a notice on the Mt. Gox Web site, CEO Mark Karpeles now says that the firm has found an old-format wallet dating back to before June 2011 which contains 200,000 coins.
The funds have been moved to offline storage and lawyers for the exchange operator have notified the court about the find, which take the number of missing bitcoins down to 650,000.
Mt. Gox says that it lost the bitcoins - 750,000 of which belonged to customers - after a software bug let hackers plunder accounts. This week an update to the 'Bitcoin Core' software has been released which aims to fix the "transaction malleability" issue.