The Central Bureau of Investigation (CBI) on Thursday filed its second First Information Report (FIR) against unidentified police and revenue department officials in connection with the May 22 firing on anti-Sterlite protestors in Tamil Nadu’s Thoothukudi district. As many as 13 people were killed in the firing on residents protesting against the proposed expansion of a Sterlite copper plant over pollution concerns. The first FIR in the case was registered on October 8.HT has seen the FIR, which was filed following the Madras HC’s August 14 order asking the CBI to probe the firing within four months. The court had questioned the state’s inaction against the police. The CBI has slapped charges of criminal conspiracy, robbery, dacoity and disobeying the law to cause injury against the unidentified police and revenue department officials allegedly responsible for the firing.Also read | Govt, not selection panel, empowered to appoint CBI chief: Centre to Supreme CourtThe case has been registered on the basis of the CPI (Marxist) district secretary K Arjunan’s complaint. “Perusal of written complaint dated May 29, 2018, discloses prima facie commission of offence...by unknown persons and public servants from police and revenue department,” the FIR said. The 13 people were killed when the police fired on the protestors on the 100th day of protests seeking plant’s closure.