A mainland man arrested in a stolen pleasure craft after a high-speed sea chase off the Po Toi Islands early yesterday could be part of a wider syndicate behind a string of boat thefts, according to police. Officers from the anti-smuggling taskforce believe the man, aged 39, who was heading for Guangdong in the boat which had a powerful 150 horse-power engine, may have previous knowledge of the area. Two police patrol boats from the taskforce gave chase to the five-metre speedboat after it was spotted off the Ninepin Group of islands shortly after midnight yesterday. After a 20-minute chase the speedboat, worth about $170,000 and owned by a Hong Kong businessman surnamed Kong, was stopped and boarded by armed officers.