Troubled Bitcoin exchange Mt. Gox, once the largest of its kind, has filed for bankruptcy protection, the Wall Street Journal reports.

At the Tokyo district court today, a lawyer for Mt. Gox announced the move and said the company has an outstanding debt of about 6.5 billion yen ($63.6 million).

Mt. Gox disappeared from the Internet earlier this week amid rumors that it is battling insolvency. Subsequently, CEO Mark Karpeles told customers on the Mt. Gox homepage that he was “working very hard with the support of different parties to find a solution” to the exchange’s various issues.

The exchange has consistently traded below the market valuation for months due to security concerns — and recently it completely froze withdrawals, sending prices on the exchange crashing as customers worried about the future of Bitcoins stored in Mt. Gox. What was more, a document claimed to have been leaked out of Mt. Gox was circulating within the Bitcoin community earlier this week, which suggested that 750,000 Bitcoins belonging to the company’s customer base had been lost.

Filing for bankruptcy protection will no doubt add on to those concerns — and cast a shadow on the future of Bitcoin. Pre-empting such a response, the heads of six of the world’s biggest Bitcoin exchanges earlier penned a letter in response to reports of Mt. Gox’s impending insolvency.

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