Illegal transactions using UnionPay terminals in Macau reached a total of MOP 2.1 billion (US$262.8) in 16H1.
According to Lusa, which cites data from the Judiciary Police (PJ), the total is near double the amount calculated for the full year of 2015 (MOP 1.2 billion).
The PJ said that most cases reported have occurred either inside the gaming resorts or at the stores surrounding the casinos, which have resulted in the arrest of 31 people, the majority being from mainland China.
In May, in an attempt to crackdown on money-laundering, Macau banks have been requiring some merchants to upgrade Union Pay terminals to ones that contain ID readers.
As well as this, Mainland customers using UnionPay credit cards are now required to produce identity cards or passports when shopping in Macau.
The moves could help the gaming hub tackle money laundering, said Hong Weng-kuan, a Macau lawyer, quoted by The Standard.