The Immigration Department has increased its investigation manpower at Chek Lap Kok airport by 50 per cent to catch travellers heading for places like Japan, the United States and Britain using fake travel documents. Officers are posing as tourists in the transit lounge to carry out surveillance and arrest bogus passport holders, who include mainlanders, Filipinos, Pakistanis and Indians. 'Some mainland stowaways first fly into Hong Kong with genuine travel documents for stopover,' a source said. 'While they await a flight to leave Hong Kong in the airport's transit lounge, members of a forged passport syndicate bring them bogus passports.' Common areas for switching passports were toilets, the smoking zone and shops. 'They then use the bogus travel documents to board flights to their destinations like the United States, where they work illegally,' the source said. To avoid detention by foreign authorities, they leave for other Asian or African countries before flying to North America or Europe. The source said this could cost up to US$20,000 for a journey to North America or Europe to find illegal employment. Bogus travel documents seized by immigration officers include fake Singaporean, Japanese and South Korean passports. Fake Hong Kong passports are understood to have been used in the past. In June this year, the department restructured its airport investigation group and set up the Anti-Illegal Migration Agency to tackle the problem. Manpower has also been increased to 61 from 41. A tactical intelligence group has been set up under the agency to boost intelligence gathering in Hong Kong and with other nations. A spokeswoman said it had also bought new hi-tech equipment to help officers detect fake travel documents at the airport. Figures showed that 2,061 forged travel documents had been seized in the first 10 months this year. About 3,094 were seized in the whole of last year. Last month, an international forgery syndicate was smashed trying to smuggle illegal Philippine labourers into Japan via Hong Kong. Officers seized more than 100 bogus documents.