Authorities said they started their investigation after noticing suspicious transactions involving three firms set up last year which claimed to be in the transport, wine and health product-related trades, but were actually shell companies.
From February last year to May this year, their banks accounts and accounts on a virtual currency exchanging platform processed about HK$1.2 billion, officers said.
Customs said the cryptocurrency transactions were very frequent, with up to 19 per day involving as much as HK$20 million per time.
Suspecting that these funds may be the proceeds of crime, officers raided four flats and a Mong Kok office on July 8, arresting four men aged 24 to 33.
Officers seized multiple computers, mobile phones and various documents during the operation, and froze HK$20 million.
“Cryptocurrency is anonymous. Its concealability is very high. So we faced huge challenges when we were investigating, especially concerning the sources of the virtual currency and who exactly owned these currency,” said Mark Woo, the head of the customs’ syndicate crimes investigation bureau.
The four suspects were not charged with a crime, however, and were released on bail.