Calcutta, July 5 :     The 48-year-old former model, Leena Sen, died a painful death between June 29 evening and the early hours of June 30 when her assailant shoved a piece of cloth down her throat, according to the post mortem report. Soon after discovering the decomposed body in Leena?s rented apartment in a multi-storeyed building near Ballygunge Phari on Saturday, the investigators had reached a provisional conclusion that she had been strangled by one or more assailants. Forensic experts, while performing the autopsy today, found a piece of cloth stuck in her throat which, they surmised, had effectively cut off passage of air into the lungs, Narayan Ghosh, deputy commissioner, detective department, said. The body was found by the police after they forced their way into the apartment to probe residents? complaint about an overpowering stench from the flat. Preliminary findings suggest she was murdered either on June 29 or 30, but forensic experts are now trying to narrow it down to a particular time and date on the basis of the report, Ghosh added. For the investigators, one crucial question relates to Sen?s nude body which does not throw any light on how and when she lost her clothing. ?The assailant appears to have pressed her mouth and nose after inserting the piece of cloth into her throat when she was in the kitchen.? Describing the murder as a crime of passion, Ghosh said the police would approach some of her friends for assistance in conducting the investigation. At this point, investigators believe the assailant, who was known to her, left the scene of crime with her clothes which, if found by the police, could have provided a key to the murder mystery. The police today seized the visitors? book maintained at the gate of the multi-storeyed building?s in-house security screen. The name of a male visitor for Sen, who had signed himself in on June 30, was found crudely erased. Another strange entry for June 29 related to Sen in the book was that of a visitor who put herself down as Supriya Sen written in Bengali in the space reserved for names, but signed as S. Ghosh in English. The police are probing the little mystery. Ghosh said residents of the multi-storeyed building had lodged a complaint with the police against Sen three years ago for allowing outsiders into her flat at odd hours. Her husband, P.K. Sen, was questioned during the day by the police. ?We got some names from him which can provide clues,? Ghosh said, adding that the relations between Sen and her mother turned sour sometime ago after her mother filed a case against the daughter on the grounds of ?breach of trust?. The mother had alleged Sen had taken away gold ornaments and valuables from her.