“The death toll from the accident has gone up to 20,” said Chhattisgarh state police spokesman R.K. Vij told AFP in state capital Raipur.
Vij said there were “over 100 labourers working on the site when the chimney fell” and that police believed that 60 to 70 more people could be still trapped under the debris.
“There is chaos at the plant. Labourers are helping the rescue team to pull people out of the debris,” Vij said.
The accident occurred when the chimney of the plant, being built by Bharat Aluminium Co Ltd (Balco), in Korba town in Chhattisgarh state, collapsed, police and company officials said.
Balco is a 51 percent-owned unit of London Stock Exchange-listed resource giant Vedanta Plc, whose activities are focused on India.
The Indian government holds the remaining 49 percent.
Television footage showed frantic rescue efforts under way to bring out those trapped by the chimney’s collapse as family members waited anxiously for news of relatives.
“Seven injured people have been brought to hospital,” Balco general manager B.K. Srivastava told AFP.
“A chimney of 275 metres was being constructed, 100 metres were already completed. There was heavy rain and lightning when the incident occurred,” Srivastava said.
Korba lies 200 kilometres (124 miles) from Raipur.
Chhattisgarh Chief Minister Raman Singh said in a statement that “a judical probe has been ordered” into the accident.
He said that a police case had been filed against Balco.