ADELAIDE, Australia, May 25 (AFP) - Police investigating Australia's worst serial killings resumed their search Tuesday for two more bodies following the discovery of nine victims in the last five days. Eight of the nine bodies found so far had been wrapped in plastic garbage bags and stuffed into barrels concealed in a disused bank vault at Snowtown, 150 kilometres (94 miles) north of here. The ninth was buried in the backyard of a house which had been rented by one of the alleged killers in the Adelaide suburb of Salisbury North. Police, who are convinced that the group murdered at least 11 people in the last six years, on Tuesday resumed searching other locations for two missing people still unaccounted for. Detectives ruled out any link between a skeleton found in Adelaide Tuesday although they are treating it as a separate homicide. Police believe some of the victims may have been killed for their fortnightly pension cheques, but have not established a motive common to all of the victims because not all were social security recipients. However they have ruled out sex motives. "Drugs, organised crime, paedophilia and sex-related things are certainly not the focus of investigations," said Detective Superintendent Paul Schramm, head of the 33-person task force investigating the murders. Three men, John Justin Bunning, 32, Robert Joe Wagner, 28, and Mark Ray Haydon, 40, have been arrested and charged in connection with the murders. The victims were people with whom they are alleged in some cases to have been intimately linked in what police say was a shrinking circle of associates preying on each other. Schramm could offer no logical explanation for the crimes but said Australia "is a complex society and from time to time these things happen." The three men charged are friends from Adelaide's northern suburbs and the remains of Haydon's 37-year-old wife, Elizabeth, are thought by police to be among those found in the vault. Neighbours and friends of the family told reporters Elizabeth Haydon was a woman who had a tough upbringing and a hard life. She had eight children aged between 21 and 11 from a string of unhappy relationships. But she appeared to be getting her life back together in the longest relationship she had ever had, and was fighting to keep her two youngest children when she disappeared last November. "When they said she disappeared I knew she hadn't gone of her own free will because she fought for so long to keep her boys," her sister Christine Spek told reporters. The other victims formally identified so far include convicted paedophile Barry Wayne Lane Australia's previous worst serial murders were of seven backpackers, mostly European tourists, whose bodies were found in a forest south of Sydney between 1989 and 1992. Roadworker Ivan Milat is serving life for the murders.  