Narain Singh, domestic help of Sunanda's husband and Congress MP Shashi Tharoor, driver Bajrangi and family friend Sanjay Dewan, today agreed to face the lie-detector test sought by Delhi Police to verify certain evidence in the Sunanda Pushkar murder probe. 

Delhi Police had moved a plea before a magistrate in the Patiala House Court last week seeking permission to conduct polygraph test on the three witness.

Police have accused the three of concealing "material facts" like a power cut in room no. 345 at Leela Hotel on January 17, 2014 around 7 PM where Pushkar was found dead around 8 PM. Sources close to the investigation said that once polygraph test is conducted on these three persons, police are likely to seek similar screening of around a dozen witnesses in the case. 

"Investigation is done as per an action plan. The Investigating Officer keeps reviewing his evidence he gathers during the probe and whatever necessary, is done. At this juncture we will not like to speculate (about Tharoor) but there is nothing to be read in this," Delhi Police Chief  B S Bassi said when asked if Tharoor will be questioned again.

Tharoor has been questioned thrice in this case so far. Sunanda was found dead in the hotel suite on January 17 last year, a day after she was involved in a spat with Pakistani journalist Mehr Tarar on Twitter over the latter's alleged affair with Tharoor.

In January this year, police claimed that Sunanda Pushkar (51) was poisoned, and registered a murder case against unknown persons. A Special Investigation Team (SIT) which has been formed to investigate the case is also looking into a possible link to the multi-million dollar Indian Premier League.