Tokyo-based Bitcoin exchange MtGox, which declared itself bankrupt last Friday after losing 750,000 customer Bitcoins, and 100,000 of its own, worth a total of £300m.
In a statement, the company said that “the abuse of a bug in the bitcoin system” had led to an “increase in incomplete bitcoin transfer transactions”, adding that there was also “a possibility that bitcoins had been illicitly moved through the abuse of this bug”.
But when referring directly to the total of 850,000 Bitcoins that have now gone missing, the company admitted that “there is a high probability these these bitcoins were stolen as a result of an abuse of this bug”.
“An expert” has now been asked to “look at the possibility of a criminal complaint and undertake proper procedures”. MtGox says it will “make all efforts to ensure that crimes are punished and damages recovered”.
But MtGox says it must be allowed to continue trading in order to “increase repayments to [its] creditors”.
Japanese finance minister Taro Aso told Reuters that it was still unclear whether the situation at Bitcoin “was a crime or just theft”.
“We still have not had a clear grasp of the situation,” he said.
MtGox started life in 2009 as an internet-based exchange for trading card game “Magic: The Gathering”. It was sold by founder Jed McCaleb in 2011 as the company began to move into Bitcoin.
The buyer, Mark Karpeles, built MtGox into a business which would be handling 70 per cent of global Bitcoin transactions by April 2013.
After its first security breach in June 2011, which resulted in the theft of a large amount of Bitcoins by a hacker, MtGox became beset by problems for the next two years – including being subject to new anti-money laundering requirements by e-payment network Dwolla – as Bitcoin value fluctuated and the currency found its feet in the world economy.
But it was February 2014 when the “bug” was discovered that could let individuals alter transaction details to give the appearance that Bitcoin transfers never went through, when they actually had.