Mt. Gox, the Tokyo-based digital currency exchange that filed for bankruptcy protection last month, said it had located about 200,000 of the 850,000 Bitcoins it said had gone missing.

The company said in a statement posted on its website yesterday that it had notified the Japanese court overseeing its reorganization of the discovery. It said the cache of Bitcoins was found in one of the exchange's old-format electronic "wallets" on March 7 and has now been moved off-line for security reasons.

The company said its revised count of missing Bitcoins, 650,000, may change depending on the results of an investigation.

Mt. Gox said Feb. 24 it lost 750,000 Bitcoins belonging to users and 100,000 more of its own, which were valued at about $500 million at the time. The exchange said in a statement that its debt exceeded assets by 2.7 billion yen ($26.4 million.)

Since Bitcoins exist as bits of software, they can be stolen if a hacker gains access to the computers and servers used to run online exchanges, where the virtual currency can be traded for dollars, euros and other currencies. "There is a high possibility that the Bitcoins were stolen," Mt. Gox said in a statement when it filed for bankruptcy.

The exchange started as a marketplace for illustrated trading cards used to play the game Magic: The Gathering. It is under investigation by prosecutors and regulators examining the use of the digital currency.

Bitcoin was introduced in 2008 by a programmer or group of programmers under the name Satoshi Nakamoto and has since gained traction with merchants around the world. The digital currency has no central issuing authority, and uses a public ledger to verify transactions.

The underlying software has undergone numerous versions since first released in 2009. Mt. Gox, in turn, used its own custom implementation of the Bitcoin software to serve its customers.

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