Congress MP Shashi Tharoor on Sunday returned to the national capital, saying it is his duty to cooperate in the investigation into the death of his wife Sunanda Pushkar even as Delhi Police said it will not question him as of now.”It is my duty to cooperate with the police investigation and not to undermine the probe in any way,” said Tharoor while heading back to Delhi on a flight from Kochi after a fortnight-long stay for Ayurveda treatment at Guruvayur.A senior Delhi Police official said they were not going to question Tharoor for now as they want to first examine all other people related to the case and look into the available evidence.”As of now we have no business with him. We would like to question his aides and others including the hotel staff. We would like to collate all the available material relevant to the case and then take a decision on the issue of examining him (Tharoor),” he said.However, according to reports, the Delhi police are soon likely to question Pakistani journalist Mehr Tarar.Another official associated with the probe said that in a couple of days, they will move “letter rogatory” in a local court under sections of CrPC for sending viscera samples to a foreign lab in the US or UK to determine the nature and quantity of the poison which caused her death.”A letter rogatory or a letter of request is a formal request from a court to a foreign court for some type of judicial assistance. The Indian court will request the court of the country where the viscera has to be tested to get it tested in their lab. After tests, the lab will send the report to their court which would be routed to our court,” he said.Meanwhile, Congress MP Sashi Tharoor on Sunday (January 11) met Ahmad Patel, political secretary to Congress president Sonia Gandhi, during which the issue of Delhi Police filing a murder case in his wife Sunanda Pushkar’s death was briefly discussed.Highly placed sources in the party said that Tharoor had sought an appointment with Patel two days ago.While the issue of registration of a murder case in Sunanda’s death came up for discussion briefly, the two leaders also discussed prevailing political scenario and recent developments in Kerala, from where Tharoor is elected to Lok Sabha.There is little likelihood of any meeting of Tharoor with Sonia or Congress Vice President Rahul Gandhi in days to come, the sources said, adding nothing has been decided on further course of action against Tharoor vis-a-vis party affairs so far.Party general secretary Janardhan Dwivedi had two days ago said that there should be no discrimination either in someone’s favour or against in the investigation.