Union Minister of State for Human Resource Development Shashi Tharoor was admitted to All India Institute of Medical Sciences after he complained of chest pain, say sources.
According to a Times Now report, Tharoor has been shifted out of the Intensive Care Unit (ICU) of the AIIMS hospital.
Tharoor's wife Sunanda Pushkar was found dead at the five-star Leela Hotel in South Delhi on Friday night. Her body was found on a bed in suite 345 of the Leela Hotel.
Her death comes within 48 hours of her going public about her husband's alleged affair with a Pakistani journalist, Mehr Tarar, raising suspicions of suicide, although no note has been found.
She was discovered by Shashi Tharoor when he returned to the hotel on Friday evening after Friday's AICC session. The couple are said to have moved out of the minister's official bungalow as it was being painted.
The police have initially suggested it was suicide. But late at night, the officers were more guarded. Police sources said it could be a "natural or unnatural death". They said all angles were being probed: suicide, poisoning and death due to a sudden heart attack.
A forensic team is at the hotel. A magistrate was interrogating Shashi Tharoor and his private secretary as per media reports.
The case is being probed under Section 176 of the Criminal Procedure Code as the marriage was less than seven years old. Delhi Police will also ask Twitter to give details of direct messages between Sunanda and Tarar.