Vedanta Ltd said on Wednesday a sulphuric acid leak from a tank at its southern Indian copper smelter was severe and inaction could lead to serious environmental consequences.
The district administration had said on Sunday the leak at the plant in the seaside town of Thoothukudi was minor, and steps were being taken to empty the storage tanks as a safety precaution.
"There is a severe leakage in the pipe flanges and ... the pipe flanges are submerged in the acid pool collected in the dykes around the acid storage tank," the company said in a petition to the Madras high court.
The Tamil Nadu state government ordered a permanent closure of the plant and disconnected the power supply last month following protests over alleged pollution that turned violent and culminated in the police opening fire on protesters, killing 13 of them.
Vedanta, the Indian subsidiary of London-listed Vedanta Resources, said it sought a limited reconnection of the electricity supply for maintenance to guard against a potential loss of life and damage to air and groundwater.
"There is a grave risk and danger as there are other tanks and there are flammable chemicals and materials within the plant area," it said.
However, the district's top administrative official Sandeep Nanduri stuck to the earlier view that the leak was minor.
"That is their version, and this is ours. However, we are completely evacuating the sulphuric acid from all tanks as a safety precaution," said Nanduri.
Activists and residents have demanded a permanent shutdown of the plant, which they said was causing air and water pollution. Locals and activists see the smelter as a risk to fisheries. Vedanta says the protests are based on false notions.
Police said on Wednesday they had arrested about 50 people over the past week, taking the total to 254 for rioting and causing damage to property. Some people said they were being unfairly targeted over the protests and there was an atmosphere of fear in the town and surrounding villages.
Naseeba Bhanu, from a village 115 km from the town, said she had only learnt from a television news bulletin that her husband and two sons, who had taken part in the protests, had been arrested under the National Security Act, which gives police the authority to detain people without charge for up to a year.
Police officer Murali Ramba said things were returning to normal after the violence that erupted last month, the most serious anti-industrial action in years in India.
"Women were sleeping outside their houses till 2 days ago, fearing late-night raids. They have gone back to sleep in their houses after we assured them there was no reason to fear," he said.
The smelter, which has been shut for about three months, accounted for over a third of India's refined copper production and employed over 3,000 people. The company plans to appeal the government's move to shut the plant.