A three-member team of CBI was interrogating Nazrul at his office at Bhawani Bhawan in Kolkata.
Nazrul had earlier said that he was a witness to the alleged threats by officers of the Kolkata Police to Sadiq, one of the witnesses to the marriage of Rizwanur and Priyanaka Todi, daughter of industrialist Ashok Todi.
"Sadiq came to me because he was afraid that either the police or the Todis might kill him. When he was sitting in my room, Krishnendu Das, a sub-inspector of anti-rowdy section of the Detective Deaprtment of Kolkata Police, threatened him over phone," Nazrul had told the media earlier.
"I even spoke to Das and told him not to do so," Nazrul had said, adding that he was ready to cooperate with the police if they thought that his experience would help them in their investigation.
Neither the Kolkata Police nor the state CID, which investigated the death of Rizwanur before the CBI probe began on a Calcutta High Court order, recorded Nazrul's statement.
The body of Rizwanur was found on the railway tracks on September 21. It is alleged that senior officers of the Kolkata Police had tried to separate Rizwanur from his Hindu wife.
