New Delhi, Jan 18 (IANS): A drug overdose could be the reason for the death of Sunanda Pushkar, wife of junior HRD Minister Shashi Tharoor, in a hotel here, police sources said Saturday.

"It could be a case of drug overdose but things would be clear only after the detailed autopsy report," the sources said, adding it could be an overdose of sleeping pills.

Sources revealed that the couple had "verbal spat" during their flight from Thiruvananthapuram to Delhi.

In the hotel too they were arguing, which was disclosed by the house keeping staff to police during investigation.

"The hotel's housekeeping staff said that the couple were seen arguing in the lobby," the police sources told IANS.

Sunanda Pushkar was found dead under mysterious circumstances in her room at The Leela Palace hotel in south Delhi Friday.

Her death came barely 24 hours after she and Shashi Tharoor declared they were "happily married" following public airing of tweets that hinted at an extra-marital relationship and the alleged involvement of a Pakistani woman.

Tharoor, who complained of chest pain, was admitted in the same hospital few hours after Pushkar's death. He was discharged in the afternoon.

Pushkar was cremated in the evening.