Two of them sustained 5 per cent burns, while the rest had 15 per cent injuries and there was no danger to their lives as the acid was in diluted form, he added.

The official maintained it was an industrial accident and had nothing to do with the structural nature of the factory. All safety and first aid precautions were followed immediately after the accident, he said.

The copper-smelting factory makes 3.5 lakh tonnes of sulphuric acid per annum as a byproduct, in line with environmental norms that emission of sulphur-di-oxide should be minimised.

Meanwhile, Marumalarchi DMK leader Vaiko, an anti-Sterlite campaigner, said the plant be orderedto close down immediately, as it was unsafe to workers and the environment. Reports received from Tuticorin said a contract labourer of the unit also sustained injuries. The police, who have registered a case, said all the six injured had been admitted to a private hospital.

Vaiko alleged that Sterlite's Tuticorin plant was a second-hand one, having been built with parts from a knocked-down factory abroad. He said accidents had become regular at the copper smelter unit.

On July 5, 1997, about 90 girls working in an adjoining cutflower factory, Ramesh Flowers Ltd, fainted and vomited and most of them were hospitalised. The owners of Ramesh Flowers alleged that a mysterious gas had leaked from the Sterlite plant leading to the accident.

Sterlite, on its part, alleged that Ramesh Flowers was using some prohibited chemicals in its dry-flower manufacturing, which was responsible for the accident.

On August 31, 1997, a blast in the rotary holding furnace at Sterlite exploded, killing two workers. Sterlitelost about 100 days of production due to the two incidents.

A Tamil Nadu government-commissioned independent study cleared the project to be safe from the environmental angle, while another study exonerated Sterlite from the gas leak mishap.