Police have made a major breakthrough in the investigation of a senior military intelligence officer's assassination in Colombo as Tamil guerrillas continued to target police and army intelligence officers. Police have raided a safe-house in the outskirts of the capital and arrested four people including a woman connected with the assassination of Lieutenant Colonel T.N. Muthalif, one of the main officers involved in cracking down on Tamil guerrilla activities.The suspects were produced in court yesterday and remanded after preliminary investigation revealed that guerrillas of the Liberation Tigers of Tamils Eelam (LTTE) were involved in the killing. Military academy An employee in a biscuit factory on the outskirts of Colombo, whom Tamil rebels had been promised two million Sri Lankan rupees (Dh73,400) to gather information about Muthalif's movements is among those arrested. The arrests were considered a major breakthrough as the Tigers usually carryout murders in the capital without leaving any clue. Muthalif was gunned down as he was being driven to a military academy in the outskirts of the capital on March 31.