Doctors at the AIIMS, where a three-member board of doctors performed the postmortem on Saturday, had said the death was "sudden and unnatural".
AIIMS sources said the doctors have not found any trace of alcohol in the body. But presence of Alprazolam, which belongs to a group of psychoactive drugs used as sedatives, cannot be ruled out.
Sources said Sub Divisional Magistrate Alok Sharma has so far recorded statements of eight persons, including family members of Sunanda's husband and Union Minister Shashi Tharoor, his staff and journalist Nalini Singh.
Vicky Nanjappa reports:
The drug was consumed at around 2 pm last Friday and she may have passed away in her sleep some three hours later, the report suggests.
Doctors generally recommend a maximum of two tablets of the drug in chronic cases.
The Delhi police will now have a two-pronged approach to the case. Did Sunanda consume the tablets voluntarily or was it slipped in by another person? The statements recorded before the sub divisional magistrate on Sunday suggest that she had bouts of panic attacks in the past few days, but there was nothing to show that she would kill herself.
This, however, is based on the statements made by her relatives and also Shashi Tharoor.
The veracity of the tweet which was put out by her stating that she will go laughing is, however, under scrutiny.
Delhi police sources inform that they are waiting for an official copy of the autopsy report.
“We already have found three strips of Alprax at the hotel room. Once we get the autopsy report and version given to the SDM we will summon all those close to her and investigate the matter. Prima facie it looks like a case of suicide, but we will probe other aspects as well,’ the police officer points out.
The SDM is examining the statements to corroborate the sequence of events, the sources said.
They said the SDM asked Tharoor on his reported relationship with Pakistani journalist Mehr Tarar and the controversy surrounding it.
The SDM is also examining phone records of Sunanda between 3 pm and 7 pm on Friday, they said.
Sharma has written to Delhi Police asking them to share findings of the investigation till now, the sources said.
The AIIMS doctors' panel is likely to hand over the autopsy report to the SDM on Monday, they said.
The SDM may discuss various technical details with the doctors concerned after receiving the autopsy report from them, they said.
Media reports had speculated that a combination of alcohol and anti-depressants could have caused her death.
AIIMS doctors have preserved certain "biological samples for toxicological analysis as well as visco-pathological examination."
"We have completed the whole procedure. Samples for toxicological analysis means ruling out any poison. Some pathology of the heart has been preserved by us," said Dr Sudhir Gupta, head of the panel of doctors which performed the autopsy.
Samples of body fluids and viscera which were taken on Saturday were tested in the AIIMS Forensic Laboratory, findings of which will be submitted as the final report on Monday to the SDM.
Half of the samples have been sent to the CFSL, the reports of which will be sought only if any discrepancy in this report comes out. Then the court will order CFSL to submit their report directly to them.
With inputs from Vicky Nanjappa
Image: File picture of Sunanda Pushkar with husband Shashi Tharoor
Photograph: SnapsIndia
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