The Central Bureau of Investigation on Thursday registered a case against unidentified Tamil Nadu Police personnel and revenue department officials for the death of 13 people in police firing during anti-Sterlite protests in Thoothukudi on May 22. The agency started its investigations in October.

The CBI has charged the accused with, among other offences, criminal conspiracy, disobeying law with the intent to cause injury to people and criminal intimidation. The CBI has not named any police or revenue official in the FIR despite video evidence and complaints submitted to the agency naming a few officials.

On October 8, the investigation agency had filed a first information report against an unspecified number of persons from 20 organisations on charges that included rioting and voluntarily causing hurt with dangerous weapons. The document reproduced the contents of an earlier first information report filed at the SIPCOT police station in Thoothukudi on May 22, and was re-registered in August on the order of the Madurai bench of the Madras High Court.

In its order on August 14, the High Court had said it “fail[ed] to understand how not a single case, not even invoking Section 174 CrPC has been registered at the instance of the injured or family members of the deceased”. The court had said that an investigation in the case cannot be avoided.

The violence on May 22 followed two decades of protests by Thoothukudi’s residents and activists who claimed the smelter operated by Sterlite, a unit of the mining and metals major Vedanta, was a health hazard. The day after the police firing, the state government permanently shut down the plant.

The CBI action on Thursday came a day after environmental activists expressed disappointment with a National Green Tribunal-appointed committee’s conclusion that the state government’s decision to shut down the smelter on May 28 was illegal, improper and “in violation of natural justice”.