A home-made machine used to add value to Octopus cards has been found in a Yuen Long village house, leading to the arrest of a family of five. The discovery in Pat Heung on Tuesday was the first since the Octopus system was launched in 1997, police said. Initial investigations showed the machine had added value to 61 Octopus cards, totalling about HK$430,000 since November, senior inspector Li Ka-wai said. The MTR Corp and Octopus Cards suffered losses, police said. The machine comprised 10 electronic components of varying sizes, each weighing more than 5kg, Li said, adding that the components were stolen from the storeroom of Nam Cheong MTR station. 'The spare parts are custom-made products for the MTR Corp and cannot be bought on the streets,' he said. He said the cards were used to buy goods, mainly milk powder, which were then resold online. The five suspects are a former technician for an MTR contractor, 26; his wife, 30; father, 56; mother, 53; and elder sister, 28. Police believe the former technician had pocketed about HK$200,000. The Tsuen Wan district crime squad began its investigation in December after the MTR Corp and Octopus Cards complained about suspicious 'add-value' transactions. 'Creating an add-value machine requires insider technology or high-level technical expertise,' Superintendent Glenn O'Neill said. His officers looked into people employed by the MTR Corp or its contractors who had access to such machines. Later, the MTR Corp found 10 electronic parts had been stolen from the Nam Cheong station. Officers then identified the technician, who quit from the contractor in January after being warned about his poor work performance. The Institute of Vocational Education graduate had worked with the contractor for about a year and had access to the store room. Police seized the home-made machine, 61 Octopus cards and 35 cans of milk powder from his house and car, and another 79 cans of milk powder from a warehouse in Kwai Chung. The former technician is suspected of theft, obtaining property by deception and accessing a computer with criminal or dishonest intent. He was held for questioning last night. His family, arrested for handling stolen property, were released on bail. The MTR Corp said the detection of suspicious transactions demonstrated the efficiency of its monitoring and security. 'After this incident, we will look into whether there is any room for improvement,' its spokesman said.