Hours after his wife was found dead, the 57-year-old Union minister was admitted to AIIMS after complaining of chest pain. Sudhir Gupta, head of forensic sciences department at AIIMS said the post-mortem is being videographed to ensure transparency in the procedure.
Pushkar was found dead in her suite at the LeelaPalace hotel on Friday evening and the body was shifted to AIIMS at around 3:30 am for post-mortem.
Tharoor was admitted to the ICU of the cardiothoracic centre of the AIIMS and a number of investigations including ECG were carried out on him. The Minister was discharged at around 12 in the afternoon.
Doctors said he was brought to the hospital with a "cardiac condition" but he is stable now. Continuing investigation, police questioned a number of hotel staff and checked the CCTV footage of the lobby of the third floor of the luxury hotel where she was staying.
Sources in police said call details record as well as Pushkar's tweets were being checked. Pushkar and Tharoor had checked into the hotel on Thursday as their home was being painted.
A number of hotel staff, including those who had gone to her suite, were being questioned to corroborate the version of Tharoor and his staff.
Pushkar and Tharoor were at the centre of a raging controversy when reports emerged that she was upset over reported text and tweet messages between her husband and Mehr Tarar, a Pakistani journalist
Delhi police spokesman Rajan Bhagat said inquest proceedings have been initiated by the sub-divisional magistrate of the area. Any death within seven years of marriage is legally required to be investigated by the sub-divisional magistrate.
A spokesman for Tharoor said Sunanda's cremation would take place at the Lodhi Road crematorium in Delhi.
Meanwhile, Communist Party of India-Marxist state leader Kodieyri Balakrishnan demanded a 'comprehensive' inquiry into the circumstances in which Sunanda was found dead.
The news of her death came as a shock to people in Thiruvananthapuram, from where Tharoor contested and won in his electoral debut in 2009 Lok Sabha polls.
The police had stepped up security at Tharoor's constituency office in the city as soon as news of his wife's death in a Delhi hotel spread.
The Tharoor couple, married in August 2010, were seen together at the famous Sree Padmanabhaswamy temple during the 'Lakshadweepam' festival on January 14.
Shashi Tharoor suffers 'cardiac condition', admitted to AIIMS
Sunanda underwent check up at super-specialty hospital in Kerala earlier
Sunanda Pushkar's body shifted to AIIMS for post-mortem
Sunanda Pushkar's death: Hotel staff quizzed, CCTV video, call details under scanner