The Madras High Court on Tuesday ordered the Central Bureau of Investigation to conduct an inquiry into the police’s decision to fire at protestors demonstrating against mining firm Vedanta’s Sterlite Copper plant in Tamil Nadu’s Thoothukudi district in May.

Thirteen people agitating against the expansion of the copper smelter were killed on May 22 and May 23 – prompting the state government to permanently shut down the plant days later. Several people were arrested for rioting, burning vehicles in the premises of the collectorate, pelting stones and damaging public property.

Meanwhile, the Tamil Nadu government has moved the Supreme Court, challenging the National Green Tribunal’s decision to allow Vedanta to access the plant’s administrative unit.

A bench of Chief Justice Dipak Misra and Justice A M Khanwilkar considered the submission of the state government and posted it for hearing on Friday, PTI reported.

The mining corporation had moved the tribunal, challenging the state government’s order to close the plant. Vedanta has called the closure order and the pollution control board’s refusal to renew its operating licence “impugned and unlawful”.

For more than two decades, activists in Thoothukudi have accused Sterlite of contaminating the region’s air and water resources and causing breathing disorders, skin diseases, heart conditions and cancer. From February, there were large-scale protests against the company’s copper smelter, which had the capacity to produce 4.38 lakh tonnes of anodes per annum, or 1,200 tonnes per day.