ICAC officers and police probing the murder of millionaire businessman Tommy Chui To-yan in Singapore arrested six people in dawn raids across the territory yesterday. Four men and two women, aged between 30 and 40, were being detained at the Organised Crime and Triad Bureau (OCTB) headquarters for further investigation late last night. Those targeted in the police investigations into the killing include members of the Wo On Lok triad society. Independent Commission Against Corruption (ICAC) Assistant Director of Operations, Tony Godfrey, who led a six-man team to Singapore when Chui's body was discovered, last night said it was probable more arrests would follow today. 'It is possible that further arrests may follow. Certainly the ICAC and police investigations into this matter are ongoing,' he said. 'It was decided recently that we needed to take action against these people. 'In terms of the operation itself, we were simply their advisers because the police were taking action using their own powers.' Mr Godfrey said he was unable to disclose whether similar action might take place in Singapore or what had motivated yesterday's operations. But sources close to the police said yesterday's raids were mounted after police and ICAC officers checked all telephone calls to Singapore from Hong Kong during their investigations in the Lion City. Checks were also made in Hong Kong before 38 premises were searched yesterday. A fleet of more than 10 cars and vans carrying police and ICAC officers and break-in tools left OCTB headquarters in Causeway Bay at about 6 am. Those arrested, some handcuffed, were taken to OCTB headquarters between 9 am and 4 pm. Chui's body was found floating off Clifford Pier in March. He had been reported missing by his wife three days earlier. It was discovered that he was first killed and then had three scuba-diving weight-belts tied to him. The driver's seat of his Porsche, found in a car park, was covered with blood. Chui, 38, and his wife were involved in shipping, soft drink, cigarette, real estate and import and export businesses in Singapore. Chui, who emigrated to Singapore in April 1993, was to testify in an alleged cigarette smuggling case for the ICAC. One of the defendants in the case, Henfrey Tin Sau-kwong, faces corruption charges for offences that allegedly took place when he was a Customs officer. Tin, 45, is a friend of former ICAC deputy director Alex Tsui Ka-kit, who was sacked in 1993. His co-accused, trader Chong Tsoi-jun, 49, faces two counts of conspiracy to offer advantages in relation to the processing of export permits for cigarettes and the preferential sale of cigarettes from a tobacco firm. A third accused, former Customs officer Yeung Kam-fai, 43, is jointly charged with Tin and Chong on one count each of conspiracy to export unmanifested cigarettes worth $8.5 billion.