The brief lull has ended, and hackers are at it again.

Hong Kong-based Bitfinex was forced to halt its operations on Tuesday after discovering a security breach in the system, resulting in bitcoins stolen from some the exchange’s users. On Reddit, Bitfinex community director Zane Tackett estimated that some 119,756 bitcoins—worth more than $61 million at current exchange rates—went missing during the breach.

Bitfinex halted trading, withdrawals and deposits in all digital currencies, including ethereum, but the exchange said the breach was limited to bitcoin wallets. The causes of the breach are still unclear, but the hackers appeared to have bypassed the bitcoin exchange’s mandated limits on withdrawals.

“The theft is being reported to—and we are co-operating with—law enforcement,” Bitfinex said in a blog post. “While we conduct this initial investigation and secure our environment, bitfinex.com will be taken down and the maintenance page will be left up.”