The Special Investigation Team (SIT) probing Sunanda's case questioned Singh and Bajrangi twice in the past three days. The SIT also questioned around a dozen chemists in and around Tharoor's bungalow in Lodhi Estate, a police source said today.
"They were all questioned in light of the information emerging out of the AIIMS medical board's opinion on the FBI report in connction with the case," said the source, adding that the questions revolved around the source of drugs suspected to have caused 51-year-old Sunanda's death.
Tharoor was not subjected to the test but was questioned thrice in the case.
The AIIMS medical board, which gave its opinion on the FBI report on Sunanda's viscera and other samples, had unanimously concluded that she died of poisoning, with the presence of Alprax in her stomach.
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The board did not rule out the possibility of any injectable poison, in view of a particular mark on Sunanda's body, and said that the FBI report confirmed the presence of lidocaine in her body.
It also said that the Special Investigation team (SIT) probing the case should "thoroughly investigate" if any person had access to injectable agents in view of a syringe mark spotted in Sunanda's body.
In January last year, Delhi Police had registered a case of murder in connection with the death of Sunanda. An AIIMS medical board had found poisoning as reason for her death following which the police had sent her viscera samples to an FBI lab in US.
As police could not firm up about cause of the death based on the FBI report, they requested a medical board of AIIMS to analyse the contents of the report.