POLICE have arrested a Mercedes-driving Mr Big believed to be behind a Hong Kong drugs syndicate which has been flooding the Canadian market with heroin so powerful it has killed more than 70 addicts. The suspect, named only as Kong, will appear at Eastern Magistrates Court today to answer an extradition charge on drug-trafficking registered by the Royal Canadian Mounted Police. The tall, bespectacled, smartly-dressed 36-year-old was arrested yesterday after being invited to answer questions at the Wan Chai offices of the police Narcotics Bureau. Chief inspector Steve Carruthers said: ''We have closed in on one of the main syndicates exporting to North America. We believe he is an important figure in drug smuggling.'' It is thought Kong, who lived in Quarry Bay, is a member of the notorious Big Circle Boys triad gang, which is believed to control 90 per cent of the heroin smuggled from China. He had been under surveillance after a shipment of 6.9 kilos of grade four, 97 per cent pure heroin was discovered in a consignment of picture frames airmailed to Vancouver from Thailand on March 30. Canadian Customs officials were suspicious because the consignee's address was given as a hotel room and because the pictures, of Oriental scenes, did not appear to be worth the cost of posting them. The officers removed the drugs and installed electronic listening devices before setting up a surveillance operation next to the hotel room where the drugs were to be delivered. The Canadian police then traced a number left on a pager to a telephone in Kowloon City. This belonged to the caretaker of a block of flats who identified a resident who frequently asked to use the phone. This man, known as Chu, was arrested on April 17. He was originally charged locally for his role in assisting in drug trafficking but now will also appear before Eastern magistrates today for an extradition hearing on conspiracy to traffic in drugs. The Hong Kong police were assisted by two locally-based members of the Royal Canadian Mounted Police. One of them, Staff Sergeant Garry Clement, said a flood of almost pure heroin had killed many drug addicts in cities as far apart as Toronto, Vancouver and Montreal. ''Our priority is to go after international organisers of the drugs trade. We think this is a major breakthrough in curtailing the flow of heroin into Canada. I think it is going to have an impact in Canada.'' Kong is also being investigated by the Financial Investigation Group of the narcotics bureau. This unit seeks to trace and seize the assets of those who profit from drug-smuggling. A glut of heroin in Canada earlier this year forced dealers to compete by boosting quality and cutting prices. In May alone, more than 40 Vancouver addicts fatally overdosed on the drug. Canada is also seen as a gateway to the lucrative United States market.