The Tamil Nadu Pollution Control Board has ordered the shut down of Sterlite Industries’ copper plant in Tuticorin following a gas leak last week.

The action follows a thorough investigation into complaints of a noxious gas leak from the public on March 23, a senior district official said. The process of shutting down the plant began on Friday night.

Sterlite Industries, a Rs 41,000-crore company, is part of Vedanta Plc, which has operations in India and Australia and is listed on the stock exchanges, has denied allegations of a gas leak in a press statement available on its Web site.

The statement says that the plant was shut down for maintenance from March 21 to March 23. Moreover, the emissions were normal and within prescribed limits.

A team of government officials inspected the copper plant on March 23 and 24. District Health Officials have not found any cases of illness due to gas leakage, the statement said.

The official said the Pollution Control Board has observed that the emission from the unit had “breached limits prescribed by the Board.” Online instruments had registered the excess emissions. Officials had inspected the factory following complaints from the public on March 23.

The Pollution Control Board had sought an explanation from the company which had responded on March 27. But it found the company’s explanation “unsatisfactory”.

The Tuticorin plant has a capacity to produce about four lakh tonnes of copper annually and it is the ‘world’s lowest cost copper smelter,’ according to the company.