Indian police are treating the death of Sunanda Pushkar, wife of former minister Shashi Tharoor, as murder, nearly a year after her body was found in a hotel room.

Sunanda Pushkar’s death was “not natural and was due to poisoning,” Delhi police chief BS Bassi said.

Initially, doctors said she might have died from an overdose of drugs.

Shashi Tharoor, an Indian lawmaker who married the former Dubai-based businesswoman in 2010, said he was stunned by the news.

“Needless to say I am anxious to see this case is investigated thoroughly and continue to assure the police of my full co-operation,” he said in a statement.

“Although we never thought of any foul play in the death of my wife, we all want that a comprehensive investigation be conducted and that the unvarnished truth should come out.”

BS Bassi said the police had received a “final report” from the doctors saying that Sunanda Pushkar had been poisoned.

“The poison could have been administered orally or it could have been injected. To proceed further in this matter, we have decided to register a case of murder,” he said.

Medical samples would be sent to foreign laboratories to find out the “quantity of poison” found in Sunanda Pushkar’s body.

It is, however, still not clear what poison is believed to have been given to Sunanda Pushkar, and how she could have taken it.

There is also no clarity over the motive of the alleged murder.

Asked why it had taken the police nearly a year to treat the death as murder, BS Bassi said the doctors examining the evidence had sought “additional information” on more than one occasion, and police had provided that.

Sunanda Pushkar was found dead in a five-star hotel in Delhi on January 17, 2014.

Shashi Tharoor and Sunanda Pushkar had became embroiled in controversy over a series of Twitter messages before the woman’s death that appeared to reveal he was having an affair with a Pakistani journalist.

Sunanda Pushkar and Shashi Tharoor later insisted they were happily married and blamed “unauthorized tweets” for causing confusion.

Shashi Tharoor has repeatedly called for a swift investigation into the case.

In his statement on January 6, Shashi Tharoor added: “I join all members of Sunanda’s family in asking for full information about the basis on which the police have come to this conclusion.

“We have not been provided with copies of the post-mortem report and other reports of the inquiry… We repeat our request for a copy of these reports to be provided to us immediately.”

A former UN diplomat, Shashi Tharoor was forced to resign from his first ministerial position in 2010 amid controversy over his involvement in bidding for a cricket team.

Sunanda Pushkar had allegedly received a free stake in the Indian Premier League franchise Shashi Tharoor was bidding for.

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