The Delhi police has approached the Canada’s department of justice on Monday seeking details of the deleted chats from the mobile phones of Sunanda Pushkar and her husband and Congress leader Shashi Tharoor. The police has sent a letters rogatory to the department asking them to get details of chat messages from Research in Motion Ltd, a senior police officer said.

Senior journalist Nalini Singh had told the police that she had a chat with Sunanda in which she had mentioned that Mr Tharoor and Pakistani journalist Meher Tarar had allegedly exchanged messages that were deleted from Mr Tharoor’s phone.

Sunanda, 51, 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 Ms Tarar on Twitter over her alleged affair with Mr Tharoor.

Several persons, including Mr Tharoor, have been questioned in connection with Sunanda’s death. The police has also conducted a polygraph test on six persons, all prime witnesses in the case, including Mr Tharoor’s domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple.

In February, Ms 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 death.

The Delhi police had in January 2015 registered a case of murder in connection with Sunanda’s death. The FBI report sent to the Delhi police in November 2015 had virtually ruled out the theory of “polonium poisoning” having caused her death.

However, after Delhi police failed to draw any conclusion on basis of the findings, the report was handed over to a medical board for examination before further proceedings in the high-profile case. The medical board is yet to give its opinion on cause of Sunanda’s death.