The Sunanda Pushkar murder case will be handled by a Special Investigation Team (SIT), says Delhi Police Chief BS Bassi.

In a sensational twist to the death of Shashi Tharoor's wife Sunanda Pushkar, Delhi Police on Tuesday registered a murder case on the basis of a medical report that concluded her death was unnatural and due to poisoning but nobody has been named as a suspect as yet.

Bassi did not rule out questioning Tharoor, now a Congress MP and a former union minister.

It was not clear whether she had consumed the poison on her own or it was administered forcefully or by injection, he said.

According to police sources, one among the many queries sent to the AIIMS autopsy board for clarification was if Pushkar's death appeared to be a case of "homicide" or "suicide". The board in response reportedly told the police that homicide cannot be ruled out as the sudden and unnatural death occurred due to poisoning.

"Stunned" by the Delhi police action, Tharoor, who had married Sunanda in 2010, sought full details from the investigators on the basis of which the police action came.