POLICE have launched a probe into the possible murder of Pauline Holgate Sham Po-ling. Two months ago, Clive Holgate made a statement to police about his wife's disappearance, and was later released on his own recognisance. No charges were laid and the former surveyor remains on police bail. Now detectives believe somebody killed his wife. Sham is one of three witnesses wanted for interview by the ICAC or police who have died or disappeared. ICAC investigators were eager to interview Chow Ying-kit when he jumped to his death from a building in Hunghom on May 18, 1993. And Sergeant Wan Hok-shing, a close friend of the missing woman, vanished before police investigators had a chance to question him. Sergeant Wan left Hong Kong for China in March 1994 during a two-week holiday - and never returned. Sham was first reported missing on February 1, 1992, eight days after she vanished. Her husband said he did not rush to the police because he was used to her sporadic absences and all-night gambling sessions. 'For two or three days I wasn't overly concerned,' he said. The former surveyor said he only began to suspect something was amiss when his mother-in-law Kwan Wai-king telephoned in a panic. Sham had made a habit of contacting her mother at least three times a day. But more than 48 hours had passed without a word or a visit. However, another five days of inactivity followed Holgate's conversation with Ms Kwan. He said he continued to delay his report out of a mistaken belief that the Missing Persons Unit would not begin investigating until she had been gone a week. Asked where he got that impression, he replied: 'When I was living in the UK, I understood that was the situation, so I assumed it was the same out here.' Holgate and 12 other people were detained in raids on 52 premises in July 1993. He was immediately suspended from duty, said ICAC acting Director Daniel Li Ming-chak. Holgate was re-arrested on November 4 last year, at the conclusion of an ICAC investigation. He appeared in court for the first time on November 7 last year.