Authorities in South Korea have shut down an online gambling site that deals with local stock price index, local media reported.

According to the Korea Joongang Daily, police recently arrested two people that ran the website in which members wager on how much the Korea composite stock price index (Kospi) 200 might rise or fall.

One of the arrested was the CEO and website manager, while the other man handled the site’s call center. Investigators said the two ran the site for one and a half years, taking in a total of KRW4.6 billion ($4 million) in earnings.

Police officials said the site started its operations in October 2014 from a studio flat of the CEO, a man surnamed Kim. Aside from the gambling site, Kim also developed his own trading system that he used for financial and stock transactions.