Macau authorities have detained five police officers for allegedly allowing mainland Chinese gamblers to illegally enter the special administrative region.

On Friday, media outlets reported that Macau’s Judiciary Police (PJ) had arrested five active members of Macau’s Public Security Police Force and another officer who’d recently retired. A further six officers were arrested but subsequently released without charge.

The six officers who remain in custody have been charged with corruption, running a criminal organization and misconduct by a public official. The officers are said to have charged gamblers fees to enter and leave Macau without going through proper channels, while also charging them for transportation and protection while they were in Macau.

The total fee charged per gambler for these services reportedly came to MOP 220k (US $27,400). The PJ estimated that the scam netted the officers a total of MOP 1.8m ($220k) over a four-year period. The arrests follow the recent detention of a local immigration officer suspected of charging gamblers for similarly unauthorized travel to and from Macau.