Delhi police has received the medical board's 'advice' on the FBI lab report on viscera samples of Sunanda Pushkar to identify the cause of her death.

New Delhi: In the latest development in the Sunanda Pushkar case, Delhi Police Commissioner BS Bassi told mediapersons on Friday that her death was not a natural one.

"One thing is clear that the death was not natural. It was unnatural as per our investigation till now and evidences collected so far. I can say that with certainty," Delhi Police Commissioner Bassi told reporters.

In January 2015, 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 Washington in 2015.

There was earlier speculation that Sunanda may have died as a result of poisoning through radioactive substances.

The FBI had sent its report to Delhi Police two months back. The report said the radiation levels in Sunanda's viscera samples were "within the standard safety norms" besides mentioning other details.

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.

"The medical board has submitted to us 11-page report with 32 pages of annexures which are to be examined. They have mentioned about certain conclusions which are now to be investigated," Bassi said.

CNN IBN reported that the FBI report confirms the initial autopsy report submitted by the All India Institute of Medical Sciences (AIIMS) that Pushkar's cause of death was poisoning.

"I have no knowledge on the mention of any dangerous chemical in the FBI report. The FBI report had said none of the samples contained any radioactive material. I can confirm there's no radiaoactive material but certain other findings are there. We had given the entire report to the medical board which has examined and gave us a report.

"FBI report had said that radioactive levels were within acceptable range. It had ruled out the radioactive angle. Certain other chemical compounds were found by the FBI lab. The medical board has given certain conclusions. We will investigate those," Bassi said.

The Delhi Police Commissioner on Friday held a meeting which was attended by the Special Investigation Team (SIT) probing the case. Special Commissioner of Delhi Police (Law and Order) Deepak Mishra briefed all about all related angle in the case.

Sunanda was found dead inside her suite at a five-star hotel in New Delhi in January 2014, a day after she was involved in a spat with Pakistani journalist Mehr Tarar on Twitter over the latter's alleged affair with Tharoor, the Congress MP from Thiruvananthapuram.

The investigators have so far conducted polygraph test on six persons, all prime witnesses in the case, including Tharoors' domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple. Tharoor was not subjected to the test but was questioned

thrice in the case. Sunanda's son Shiv Menon was quizzed by the SIT on 5 February, 2015.

With inputs from PTI