Former Inspector General of Police (IG) Arun Kumar Gupta and DIG, Midnapore range, Natarajan Ramesh Babu, were among the police officers interrogated today, said CBI sources.

The agency added that they were preparing to submit the report to the High Court.

The CPM leaders who were interrogated on Thursday include Himanshu Das, Bijan Roy, Rabiul Hussain and Jaideb Paik, an agency source said.

The CBI, after taking charge of the investigation into the firing, had arrested 10 CPM activists for possession of arms on March 17. The probe was then handed over to the CID. But as the CID failed to frame chargesheets against them, the 10 activists were released on bail.

In the second phase, the CBI was again given charge of the investigation in November last year. But after initiating the probe, the investigating officers could not trace the 10 CPM men.