Story highlights Mark Karpeles was detained Saturday

Mt.Gox was one of the world's largest bitcoin exchanges until last year

(CNN) Japanese police have arrested the head of the Mt.Gox bitcoin exchange company over the loss of a "massive amount" of the virtual online currency.

Mark Karpeles was detained Saturday, the Tokyo-based company said in a statement.

He is suspected of accessing the exchange's computer system and falsifying data to change the outstanding balance, Japan's Kyodo News Agency reported ,citing the Metropolitan Police Department.

A day earlier, a report emerged that Karpeles was going to be arrested, prompting him to send a message to The Wall Street Journal describing the allegations as "false." He told the paper that he planned to deny them.

Mt.Gox was one of the world's largest bitcoin exchanges until February last year, when it stopped investors from accessing money after becoming the target of online hackers.

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