The officers of the CID, a state government investigating agency, on Thursday interrogated Jahangir Sheikh, a prime accused in the March 21 Bogtui carnage and the sole witness in CBI custody when co-accused Bara Lalon Sheikh was found dead on December 12 at the central agency’s Rampurhat camp office.

The CID’s homicide wing, which has taken over the investigation of the alleged murder of Bara Lalon Sheikh in CBI custody, reached the Rampurhat sub-correctional home on Thursday afternoon with a videographer and interrogated Jahangir for over an hour.

“Jahangir was interrogated in the first round today (Thursday) and we will question him again to know if he knows all that happened on the day of the death of Bara Lalon in CBI custody,” said a CID official, adding that Jahangir was “cooperative”.

Debarshi Dutta, the CID investigating officer, on Thursday appealed before Rampurhat court for permission to interrogate Jahangir, who is now in judicial custody in the Bogtui carnage after completing six days in CBI custody.

“Jahangir was the only person who may reveal what happened inside the camp office on December 12 as there were no other people apart from CBI officials there... So, he is very important for the case,” said a source.

The custodial death of Bara Lalon put the CBI in a spot after the deceased’s wife Reshma Biwi lodged a murder complaint against seven CBI officials, including officers not connected with the carnage case such as the SP, DIG and investigating officer of the cattle smuggling case. The CBI has already moved Calcutta High Court that asked the CID not to take coercive action against the accused sleuths of the central agency.

“CID officials appealed to the court explaining the need to interrogate Jahangir at the sub-correctional home in connection with the alleged murder in CBI custody. The court granted them permission,” said Surajit Sinha, an assistant public prosecutor of Rampurhat court.

CID sources said they videographed the interrogation of Jahangir and everything related to the probe of the alleged murder according to the high court order.

A source said the CID planned to ask Jahangir about the conduct of CBI officials toward people in custody.

Jahangir is also the stepbrother of slain Trinamul leader Bhadu Sheikh, whose killing led to the Bogtui massacre in which 10 persons died. CID sleuths will meet Reshma for her statement as she has charged CBI officials with torture and extortion.

As part of the CID probe, a forensic team on Thursday visited the CBI camp office and collected samples from the bathroom where Bara Lalon’s body was found. CID officials tested if the shower pipe, from which Bara Lalon apparently hanged himself, could bear the weight.