Three scammers were caught red-handed early on Monday trying to cheat a mahjong parlour by fitting microchips to tiles and tampering with an electronic game table. Officers seized two sets of tiles, electronic components, tools, a laptop computer and a remote control device at the Tai Hang Li mahjong parlour in Temple Street, Yau Ma Tei, after arresting the three visitors from mainland China. A veteran policeman said it was the first time the technology had been used in such a crime in Hong Kong. The mainlanders were trying to modify the circuit board of an electronic mahjong table A police source A cleaner in her 50s was also picked up at the scene shortly before 3am. A police source said the Hong Kong employee let the three mainlanders – two women and a man aged 26 to 41 – enter the parlour in return for letting her off a debt. The ruse came to light when they were captured by surveillance camera and their movement activated a security system connected to the mobile phone of the owner of the parlour, which closed at midnight. He called police at 2.45am and the four were arrested outside. One of the women was understood to be a regular customer. “Initial investigations showed the mainlanders were trying to modify the circuit board of an electronic mahjong table on the premises,” the source said. He said the laptop computer was probably used to upload a programme into the circuit board. It is understood that with microchips embedded in the tiles, a scammer posing as a customer could control the shuffle in his favour. The table was designed for high-stakes games. Two sets of mahjong tiles were taken away for examination. “Police will examine those to see if they have been modified or installed with magnets or microchips,” the source said. The four were still being questioned at Tsim Sha Tsui police station on Monday. None had been charged. In previous mahjong scams criminals used tiles marked with invisible ink that could only be seen with special contact lenses or spectacles. This method was made famous by the 1989 film God of Gamblers , starring Chow Yun-fat. In June a mainland visitor accused of using special contact lenses to see such marks was caught cheating by fellow players in Lok Ma Chau.