Pakistani journalist Mehr Tarar, who fought with Sunanda Pushkar on Twitter, questioned by Delhi Police

Pakistani journalist Mehr Tarar, who was involved in a spat over Twitter with Congress leader Shashi Tharoor's wife Sunanda Pushkar hours before her death, has been questioned by Delhi Police in connection with the murder case.

Tarar's questioning took place in February at a place of her choice -- a prominent hotel in New Delhi. She was questioned by the Special Investigation Team (SIT) probing the case in the presence of women police personnel, sources said on Monday.

Summons could not be issued to Trar as she is a Pakistani national but she had earlier stated that she was open to joining investigation into the matter and had also written to a senior official communicating the same.

51-year-old Sunanda was found dead at a suite in a five-star hotel in South Delhi on the night of January 17, 2014, a day after her spat with Tarar on Twitter over her alleged affair with Tharoor, the Congress MP from Thiruvananthapuram in Kerala.

Tarar was questioned about her relation with the Congress leader and his wife, her fight with Sunanda over Twitter, and other issues revolving around Sunanda's mysterious death. So far she has refused any proximity on personal terms with both Tharoor and Sunanda, the sources said.

The questioning stretched beyond two hours and Tarar was also asked to fill a questionnaire prepared by the SIT, they said.

Tarar also figured prominently in a statement by journalist Nalini Singh, believed to be the last person to have spoke to Sunanda over phone hours before her death.

Singh had said that Sunanda had mentioned to her about Tharoor deleting Tarar's messages from his Blackberry phone and had asked her if she could help her in retrieving the same. Singh had further said that Sunanda also told her she was unhappy following a meeting between Tharoor and Tarar in Dubai.

In January 2015, Delhi Police had registered a case of murder in connection with the death of Sunanda. An AIIMS medical board had earlier found poisoning as reason for her death following which the police had sent her viscera samples to an FBI lab in US.

The FBI lab report, sent to Delhi Police In November 2015, endorsed the findings of the AIIMS Forensic report. As police could not firm up about cause of the death based on the FBI report, they requested a medical board of AIIMS to analyse the contents of the report.

Several persons including Shashi Tharoor have been questioned in connection with Sunanda's death.

The police have also conducted polygraph test on six persons, all prime witnesses in the case, including Tharoor's domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple.