As police probe circumstances leading to Sunanda's death at a city hotel, the on-board fight points to differences that clearly persisted despite the couple's joint statement that claimed their marriage was intact. 

This open display of differences between the couple, sources said, was seen by I&B minister Manish Tewari, who sat across the aisle from the couple. Tewari boarded the flight at Mumbai where he had attended a function. 

Piecing together details of what happened in the aircraft and at the hotel, police feel the Tharoors virtually fought non-stop for about 72 hours over Tarar before Sunanda's death. "Differences had been brewing over six months but aggravated in the last two. She was extremely depressed and angry in her last three-four days," a source said.

Investigators will examine if the harsh exchanges between the couple became the final trigger for Sunanda's death. With Tharoor's domestic help Narain telling police arguments between the couple had indeed turned violent, police are awaiting the autopsy report. Her body reportedly had scratch marks and bruising behind the wrists. 

Tewari was a witness to the events on board the flight and police sources said he had sought to calm things down. Bur sources close to the minister said he did not intervene at any stage. At the airport the spat apparently continued and Sunanda was seen rushing to the washroom in tears. Parts of the argument have apparently been captured in CCTV footage outside the airport washroom. 

Investigators said there is reason to suspect these fights may have played a role in the death. "After the airport fiasco, the couple continued arguing, possibly even on January 16 night after Tharoor moved into the hotel. After landing in Delhi, Pushkar refused to go home and went to the hotel alone. Tharoor joined her the next day," an official said. 

Indicating the argument on January 16 night may have turned violent, doctors who conducted the autopsy on Saturday on Sunanda said she had injury marks on her body. But doctors are yet to officially state the nature of injuries. 

Sunanda, it is believed, overdosed on Alprax tablets after this fiasco which lasted overnight. Empty strips of the antidepressant pills have been recovered from the room. A sub-divisional magistrate will record Tharoor's statement by Monday.