LAHORE: President Asif Ali Zardari has said that “a special group' is investigating the assassination of former prime minister Benazir Bhutto, and about “90 percent' of those accused have been arrested, while action continues against those who washed the crime scene at Liaquat Bagh, a private TV channel reported on Thursday. Zardari said the decision to approach the UN for an investigation into the assassination of Benazir was not made by him: “the Senate, the National Assembly and the four provincial assemblies decided to approach the world body for an impartial probe'. The president said his government had empowered parliament.