Singh along with Himanshu and Pooja had gone to put posters for a gathering and a candle light vigil called 'Justice for Professor Sabharwal' Sunday.

The police, who have already announced Rs.50,000 reward for those providing clues to solving the case, are now questioning Himanshu, Pooja and Saif.

Dadwal also asked Delhi Police's elite Special Cell and Crime Branch for coordination and assistance with district police to solve the murder case.

'We will not comment about who all are suspects. We are yet to reach any conclusion and the matter is being investigated,' Karnal Singh told reporters when asked if Himanshu was a suspect in the case.

The police had questioned Himanshu twice so far to corroborate sequence of crime and ascertain various facts.