Crypto exchange Bittrex was fined $24 million by US authorities on Tuesday for helping clients evade US sanctions in places such as Syria, Iran and Crimea.

It is the largest penalty ever levied against a crypto currency exchange by the Office of Foreign Assets Control, the agency said.

The Treasury Department said that Bittrex allowed customers in Cuba, Syria, Iran, Sudan and the disputed region of Crimea to trade approximately $263.5 million worth of digital currencies between 2014 and 2017.

In its statement, the US said that Bittrex should have been aware these customers were in sanctioned parts of the world due to their physical and IP addresses.

In one case, a customer in Iran gave a physical address in Iran and uploaded an Iranian passport to verify identification.

“When virtual currency firms fail to implement effective sanctions compliance controls, including screening customers located in sanctioned jurisdictions, they can become a vehicle for illicit actors that threaten US national security,” said OFAC Director Andrea Gacki in a statement.

OFAC found 116,421 apparent violations of US sanctions programmes over the three years. The company apparently did not have any internal controls in place for sanctions until October 2017.

Bittrex, based in Washington State, said it was “pleased” to settle these charges with US authorities, and noted that regulators were not asking for Bittrex to make any additional changes to its money laundering systems, which was updated after 2018.