Congress leader Shashi Tharoor may be asked to undergo a lie detector test in the murder case of his wife Sunanda Pushkar, reported NDTV. Six other people have already undergone the test, including Tharoor’s domestic worker, driver and family friend, all of whom are listed as prime witnesses, according to the report. This was after the United States’ Federal Bureau of Investigation sent back its report on Pushkar’s death to the Indian government on Tuesday, where it ruled out poisoning from polonium or any other radioactive substance.

Delhi Police chief BS Bassi told NDTV that a decision on whether to call Tharoor for questioning again will be taken after the medical board involved in the investigation gives its opinion. However, the police will require a court’s permission to conduct a polygraph test.

The story so far:

· Pushkar, 51, was found dead at the Leela Hotel in Delhi in January 2014. Her death was initially considered a case of suicide, but the Delhi Police claimed earlier this year that she had been poisoned and registered a murder case. No one has been named as a suspect so far.

· In February, Pushkar's viscera samples were sent to an FBI lab in Washington after doctors from Delhi's All India Institute of Medical Sciences concluded that the poison could not be detected in Indian labs.