Bitcoin plunged after one of the largest exchanges halted trading because hackers stole about $65 million of the digital currency.

Bitcoin slumped 5.5 percent against the dollar as of 2:30 p.m. on Wednesday in Tokyo, bringing its two-day drop to 13 percent. Prices also sank 6.2 percent on Monday, although it was not clear if that initial move was related to the hack.

Hong Kong-based exchange Bitfinex said Tuesday it halted trading, withdrawals and deposits after discovering the security breach. The exchange said it was still investigating details and cooperating with law enforcement, but acknowledged some bitcoins were stolen from its users.

"Yes -- it is a large breach," Fred Ehrsam, co-founder of Coinbase, a cryptocurrency wallet and trading platform, wrote in an e-mail. "Bitfinex is a large exchange, so it is a significant short term event, although Bitcoin has shown its resiliency to these sorts of events in the past."