District authorities have pressed several cranes to clear the debris and kept ambulances ready to take the injured people to hospital.

Chief Minister Raman Singh, who ordered a judicial probe into the tragedy, asked the police to register an FIR against the Balco management for negligence.

He has asked senior minister Brijmohan Agrawal to visit the accident site in Balco Nagar, some 250 km from Raipur, to oversee the rescue operation. The Balco aluminium complex is located in Korba town.

'It's a massive accident, we have retrieved 20 bodies so far, dozens are trapped, we are striving hard to pull out the survivors, if any, from the wreckage,' Ratanlal Dangi, district superintendent of police told IANS.

The Sterlite Industries (India) Ltd holds 51 percent stake in Balco while the remaining 49 percent owned by the government.

Sterlite has invested huge sums of money in the project to double its production capacity. Currently, Balco produces 345,000 tonnes of aluminium per annum.