Bankrupt bitcoin exchange Mt. Gox said it found 200,000 bitcoins, which were previously thought stolen, in disused electronic wallets. Another 650,000 bitcoins still remain unaccounted for.

The Tokyo-based company said in a statement posted on its website on Thursday that the 200,000 bitcoins were identified March 7 after “old format” wallets were searched as part of Mt. Gox’s bankruptcy proceedings.

The online exchange for the virtual currency was unplugged in late February as rumours of its insolvency swirled, adding to doubts about the viability of bitcoins overall. It then filed for bankruptcy protection in Tokyo and said nearly all its 850,000 bitcoins were missing, most likely as a result of theft. About 750,000 of the bitcoins belonged to people who used the Mt. Gox exchange. Mt. Gox’s problems have been a setback for bitcoin, a virtual currency that has grown in popularity since its 2009 creation as a way to make transactions across borders without third parties such as banks.