About $72 million in bitcoins were stolen in a hack of a Hong Kong-based exchange, plunging the value of the digital currency some 15 percent.
"Today we discovered a security breach that requires us to halt all trading on Bitfinex," the exchange company said in a statement posted on its website late Tuesday.
Bitfinex announced that it would also "halt all digital token deposits to and withdrawals" from the exchange.
The company said that the theft was from individual user accounts and that it was cooperating with law enforcement while looking at ways to "address customer losses."
The Bloomberg business news agency reported that Bitcoin plummeted 15 percent following news of the hack, but it later rebounded.
In 2014, the Japan-based digital currency operator Mt. Gox abruptly closed after hackers stole 850,000 bitcoins, worth $450 million at the time.
Bitcoin, introduced in 2009, is one of several so-called cryptocurrencies circulating around the world. They allow individuals and companies to make digitally coded payments using alternative currencies without incurring the fees that traditional financial companies usually charge.