The Korean Customs Service (KCS) is investigating the use of digital currencies in illegal foreign exchange business in the country.

In an official announcement, the KCS said that a total of 637.5 billion won (approximately $600 million at current exchange rate) have been exchanged illegally in foreign currencies till date, which includes transactions involving cryptocurrencies.

The announcement follows the ban on anonymous cryptocurrency trading in South Korea, which went into effect on January 30.

Providing further details, the KCS pointed out that a case in which unregistered currency exchanges remitted 472.3 billion won for customers between South Korea and Australia from March to December 2017. It said that the transactions were facilitated by cryptocurrencies, CoinDesk reported.

The KCS said that it will continue to look into the illegal foreign exchange transactions and money laundering activities, including those involving cryptocurrencies. In addition, it will also investigate the use of cryptocurrencies for the purchase of illegal and smuggled goods.