Delhi Police Commissioner B S Bassi on Tuesday said that the final medical report from AIIMS has revealed that Sunanda, wife of Congress MP Shashi Tharoor, died of poisoning but it was not clear whether it was injected or administered orally.
The report also did not mention the kind or nature of the poison while mentioning a list of possible chemicals which could not be detected in Indian labs.
Police has registered a case of murder against unknown persons in the case.
Sources said Polonium 210, a radioactive isotope is suspected to be the poison that may have caused her death.
"The viscera samples may now be sent to an FBI lab in the US or lab in UK," said a senior police official.
Earlier medical reports had mentioned 12 injury marks on Sunanda's body including an injection mark on her hand and a teeth bite.
Doctors from the medical board had visited the crime spot (suite of the five-star hotel) in the first week of November along with police officials where they examined the room and lifted samples.

After analyzing it, they have submitted the third and final report in the case on December 29.
"The medical board had maintained that the death was unnatural and due to poisoning. However, it has clearly listed a number of poisons, most of which are radioactive chemicals which cannot be detected during forensic tests in Indian labs including thallium, polonium 210, nerium oleander, snake venom, photolabile poisons and heroin," the sources said.
A Special Team which has been formed to probe the case will investigate the case from scratch.
The team is likely to question Tharoor, his relatives and personal staff along with the employees of the five-star hotel where she was found dead on January 17 last year, the sources said.
It will also examine the hotel doctor who declared Sunanda dead and go through CCTV footage of the hotel. The forensic report of Sunanda's mobile phones and laptop which were sent for tests will also be evaluated.

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