The nine men and eight women, aged between 22 and 58, were arrested on Tuesday after a series of raids in the New Territories.
The total amount was generated over a 14-month period playing a variety of games on an online casino website, including roulette, baccarat and blackjack.
The group recruited bookmakers by offering them monetary rewards to find players to gamble on the website.
The gamblers would then transfer the money into bank accounts or stored value facilities to buy points from bookmakers who helped them set up accounts.
The bookmakers would launder the money through different accounts.
Police officers also froze HK$4.5m in bank accounts controlled by members of the syndicate in the police operation code named “Deepskill.”
Mobile phones, laptops and bank cards were also seized as evidence.
According to the Hong Kong police, the syndicate had recruited thousands of gamblers in the city since beginning the operation in December 2017.
Police sources say investigations are ongoing and more arrests are possible.
