NEW YORK (MarketWatch) — Vircurex, a small virtual currency exchange, halted withdrawals of bitcoins and other cryptocurrencies Monday after large withdrawals drained its holdings. The exchange offered no details about the withdrawals other than that it follows two “incidents” last year. The news comes a month after Mt. Gox, a major trading platform for bitcoins, filed for bankruptcy, saying much of its holdings had been stolen by hackers, raising questions about bitcoin security issues. Vircurex has just 56 bitcoins traded in the last 30 days, while BitStamp traded over 600,000 during that time period, according to Bitcoin Charts. “Unfortunately we had large fund withdrawals in the last weeks which have lead to a complete depletion of our cold wallet balance,” said Vircurex in a statement, adding that it has worked out a method to gradually repay the frozen funds.