. "SIT has informed me that Amar Singh has been called in for questioning. He is being quizzed," Delhi Police chief BS Bassi told reporters.
Pushakar, wife of high profile Congress leader and former Union Minister Shashi Tharoor was found dead under mysterious circumstances in a Delhi hotel in January last year.
A special investigation team of Delhi police has started the probe after medical reports attributed Sunanda's death to poisoning.
Amar Singh had claimed that Sunanda had accepted the blame for IPL wrongdoings that took place when Tharoor was Ministers of Sports and External Affairs. There were allegations that Tharoor had "misused" his office to ensure that Rs 70 crore was paid to Sunanda.
Reports said the investigators are examining whether the IPL controversy had anything to do with Sunanda's death.
The SIT has already questioned Tharoor, journalist Nalini Singh and house hold helpers of Sunanda Pushkar.