LAST week, we revealed a Hongkong car exporter was told he would have to pay up to HK$1 million to secure the release of colleagues being detained by mainland police. His men are still under guard in Shekou without charge. This week, we present further allegations that Public Security Bureau (PSB) officials are behind what appears to be a wholesale, systematic extortion racket worth millions of dollars. Hongkong car exporters allege hundreds of vehicles are routinely held to ransom. There are reports of ''supervision fees'' being charged for ''looking after'' detained cars. No longer can these be regarded as isolated incidents committed by a few loose cannons across the border. The allegations strongly suggest that a pattern of premeditated, well-planned interceptions by PSB officials has emerged. Indeed, one car exporter claims some PSB officers make so much money, they come to Hongkong and place their own orders for luxury cars. How often have we heard senior Chinese officials claim that stamping out corruption is a top priority of the Beijing authorities? Here, surely, is a test of that resolve. If Beijing wishes the people of Hongkong to take them seriously on this issue, they should dispatch a team of investigators to Shekou without delay.