File photo of Congress leader Shashi Tharoor with Sunanda Pushkar.
Sunanda Pushkar's son Shiv Menon is likely to be questioned today in connection with her murder, Police Commissioner B S Bassi said in Delhi.
Mr Bassi said that Menon, who was out of India, has reached the national capital.
"He (Menon) was summoned. He has now reached Delhi. He will be joining our investigation, as per my information, sometime... today," Mr Bassi told reporters, adding that Mr Menon was out of India so he could not come earlier.
A police team probing the murder of Ms Sunanda has questioned at least 15 people in connection with the case so far.
Congress Member of Parliament Shashi Tharoor, his staff members and close friends were among those quizzed by the Delhi Police. Former Samajwadi Party leader Amar Singh and senior journalist Nalini Singh have also been questioned by police.
52-year-old Sunanda Pushkar was found dead in her suite at a five-star hotel in south Delhi on the night of January 17, 2014, a day after she was involved in a spat with Pakistani journalist Mehr Tarar on micro-blogging website Twitter over the latter's alleged affair with Shashi Tharoor.