THE chief suspect in the murder of a key witness in a Hong Kong smuggling case is being held in limbo in Beijing because of lack of extradition agreements. Johnny Cheung Wai-ming is wanted for murder in Singapore and for conspiracy to pervert the course of justice in Hong Kong. Privately, Hong Kong police would like to see him returned to Singapore to face the death penalty. But authorities there have backed off in their attempts to secure the unofficial extradition of Cheung, a Hong Kong citizen, because of fears of creating a diplomatic incident. There is no extradition treaty between China and Singapore. Hong Kong also lacks such an agreement, and talks are under way behind the scenes to determine the fate of Cheung, 38, who was arrested in Beijing in April, and is being detained - apparently indefinitely - over what are believed to be immigration-related matters. Meanwhile, the hunt is continuing in China for four alleged accomplices in the murder of Tommy Chui To-yan, who disappeared in Singapore in March before he was due to give testimony in an Independent Commission Against Corruption case involving an alleged $8.5 billion cigarette smuggling racket. Organised Crime and Triad Bureau sources say Cheung's future remains uncertain. 'It still looks as if he will be coming back, but when - that is a bit hazy at this stage,' said one source. 'Initially, he was going to come back quickly. But nobody knows much at the moment about his status.' Hong Kong Police Commissioner Eddie Hui Ki-on, who returns to the territory from Singapore today, has denied his trip there was linked to the case. Investigators probing Chui's murder say his killers appear to have placed keys beside his abandoned car in a pattern similar to a symbol used by a prominent Hong Kong triad society. Chui, 38, also had his limbs padlocked together before his corpse was forced into three garbage bags and dumped in the harbour near Clifford Pier. It was found a few days later. Officers say Chui, who rejected offers of protection despite being the key witness in the smuggling case, was attacked in a car park on the day he vanished. His black Porsche was rammed by a stolen Honda. Chui was abducted and both cars were left in another car park. Traces of blood were found in the boot of the red Honda Accord. Next to the Honda were three of Chui's keys, which investigators say can be matched to a Won On Lok triad society emblem. Police in Singapore have obtained information from a witness to the crash who has also identified the Honda driver from a photo-fit match. Chui's body was weighed down with scuba diving belts. But his head was left protruding from one of the bags and, although his mouth and nose had been taped, it was clear he had been badly beaten. Cheung, a former Hong Kong prison officer, was deported to the territory in 1992 after his release from jail in Scotland, where he served part of a 12-year sentence for planning a vicious attack on a Chinese restaurateur in Glasgow.