The police are checking this out with cellphone companies and the Mahanagar Telephone Nigam Limited. The police hope that this may reveal vital clues about the assailants, and, more importantly, the time when she was attacked.

The post-mortem report, says a senior police official, has approximately revealed the time of her death. ``But it does not give the exact time. Shivani's body was taken to Swami Dayanand Hospital at 7.20 pm. Going by the post-mortem report, she was killed approximately four hours earlier, plus minus half an hour,'' the official said.

He added that the post-mortem also indicates that Shivani had taken her lunch around two hours before she was killed.

So far, attempts to trace the mysterious Rajeev Bhatnagar, whose name is entered in thelogbook of Shivani's apartment block, have proved futile. The address he had noted has also turned out to be fictitious.

The police are, nevertheless, working on the possibility that this Rajeev Bhatnagar feigned his identity and address to frame someone else. ``It is likely that this Rajeev Bhatnagar and the Mr Sharma, who came with a box of sweets and wedding card are the same person. Even this Sharma's claim that he was sent by Mr Adhikari from Chandigarh has proved to be fictitious.'' said a senior police official.

He also said: ``But one or more persons could have visited Shivani after this Sharma left her house. Then, the presence of two glasses of water, two cups with tea, biscuits and dry fruits points to the possibility of familiar people visiting the house. This Mr Sharma seemed to be a stranger.''