Mt. Gox, once the dominant exchange for bitcoin trading, on Friday said more than $470 million of the virtual currency vanished from its digital coffers, kicking into high gear a search for the missing money by victims and cybersleuths.

Acting alone and in groups, the people stepped up their efforts after Mt. Gox filed for bankruptcy protection in Japan and confirmed rumors it had lost almost 750,000 of its customers' bitcoins, as well as roughly 100,000 of its own.

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