The value of bitcoin and many other digital currencies fell to their lowest levels this year after South Korean exchange Coinrail said a hack over the weekend stole virtual coin estimated to be worth more than $37 million.

In a post published Monday morning, Coinrail said hackers obtained about 30 percent of its coin and token reserves. The stolen coins included those designated as NPXS, ATX, NPER, and DENT. A wallet address reportedly belonging to the attackers showed the value of the pilfered coins was as much as $37 million. Coinrail’s statement said officials took the exchange offline and moved the remainder of its assets to cold storage as officials review the security system and work with law enforcement to investigate what happened. The statement made no mention of if or how the exchange might reimburse customers for the losses.

The price of bitcoin was trading down about 6 percent on Monday morning, according to Coinbase . As Ars reported Sunday , bitcoin had already lost more than half its value since last year’s all-time high. The price of Ethereum and many other digital currencies also fell on Monday after experiencing declines over the past month or two.

Coinrail is only the latest exchange to report it lost millions' worth of digital coins to hackers. In January, Japanese exchange Coincheck said it experienced a theft of XEM cryptocurrency valued at $400 million. Other exchanges reporting similar events in recent months include Tether and EtherDelta.

Exchanges aren’t the only ones reporting major losses. In March, researchers at 360 Netlab reported on an operation that was stealing Ethereum coins that end users were storing in poorly secured apps and mining rigs. Early Monday, the researchers said the wallet used in the hacks has now amassed more than $20 million dollars' worth of the coin.