The Madras High Court on Tuesday ordered a CBI inquiry into police firing during anti-Sterlite protests in Thoothukudi.
13 people had died in the firing that took place on May 22.
The Orders were passed by Justice C T Selvam and Basheer Ahamed.
The Court also quashed the detention orders passed against six individuals in connection with violence during the protest. They were detained under the National Security Act.
Following the firing incident, the state government had issued an order for "permanent closure" of the Sterlite copper smelter.
The National Green Tribunal recently allowed Sterlite to access administrative block. Tamil Nadu government had moved to Apex Court against the order.