Two Macau police officers are suspected of masterminding a theft of more than 4 million patacas from two Hong Kong residents on Friday night in Macau.
Four suspects, including a 30-year-old serving immigration officer and a former police officer, were arrested on Sunday in connection with the case.
A serving police officer suspected of masterminding the robbery is still on the run.
The theft of 4.6 million patacas happened at about 10.30pm, shortly after the two Hong Kong men fetched the money from an apartment in a building near the Border Gate.
The apartment is believed to be the location of an underground bank smuggling money for mainland gamblers.
At least one of the two Hong Kong victims is believed to be a junket operator at a VIP gaming hall.