FIFTEEN luxury cars worth about $7 million have been recovered by detectives in the biggest swoop of its kind in a year, following an upsurge in the theft of expensive vehicles. Organised Crime and Triad Bureau (OCTB) officers also arrested seven men in the series of raids throughout the territory, which confirmed the use of containers as the main method of transporting the stolen cars across the border. Previously, most vehicles had been smuggled to China by sea on multi-engined tai feis operating from the mainland. A police spokesman said OCTB officers launched ''intensive investigations'' following the traditional upsurge in luxury car thefts prior to the Lunar New Year. The arrests and seizure of 12 BMWs, one Mercedes and two Japanese cars were made by OCTB's A-Division, which specialised in investigating the theft of stolen luxury vehicles. ''Following the recovery of four stolen vehicles in a car-park of a private housing estate in Lam Tin on February 3, officers put a number of locations in the New Territories under close surveillance,'' a police spokesman said. ''At about 6 am on Friday, OCTB officers intercepted two vehicles with four men on board near Tan Kwai Village. ''They were arrested after a container loaded with three vehicles was found at the scene.'' In another phase of the operation, officers ambushed three men at an empty vehicle storage pound near the border at Ma Tso Lung, after ''suspicious activities were spotted inside''. During a search of the yard, police discovered two containers, each loaded with four stolen cars. The gang is believed to have specialised in stealing older model cars as it is still possible to obtain licences for them in China. Detectives believe the cars may have been destined as replacements for vehicles stolen previously but which have broken down due to a lack of maintenance. The raids followed a massive reduction in luxury vehicle thefts last year after the success of Operation Disavow which was mounted in three phases by the Anti-Smuggling Task Force to stop car-carrying tai feis from operating in Hong Kong waters. In November, the number of luxury cars stolen dropped below 10 for the first time in more than three years, but rose to 24 in December and up to 50 in January. However, the figures are still well below last year's level when thefts were running at more than 10 a day in January. Chinese and Hong Kong anti-triad police are planning their biggest joint conference to crack down on organised crime next month. The meeting, to be held in China, expands on the two forces' first anti-triad seminar in Zhuhai last June. Organised Crime and Triad Bureau chief, Senior Superintendent Albert Kwok Cho-kuen, said eight provinces were pencilled in for the seminar - a vast increase on the 1993 meeting involving only Guangdong and Hong Kong. ''We haven't fixed a date yet, but it will most likely be in March, and it will probably be in Shanghai,'' Mr Kwok said. Anti-triad experts from Hong Kong will brief Public Security Branch officers on triad tactics, pass on intelligence and make valuable contacts. ''We want to explain to them how the Hong Kong triads may be joining hands with criminal organisations in China,'' Mr Kwok said.