At least five workers were injured after a furnace exploded at a sponge iron factory, triggering a fire inside the unit in West Bengal's Paschim Bardhaman district, police said on Saturday.
The incident occurred late on Friday in Jamuria, and the explosion could be heard from nearly a kilometre away.
A senior police officer said the explosion triggered a fire inside the factory, prompting a large-scale rescue operation by the police and fire services.
"Five workers have been rescued so far and shifted to different hospitals in critical condition. It is not yet clear whether anyone else was near the furnace at the time of the explosion.
"Search operations inside the unit cannot begin until the temperature is brought down and the area is declared safe," said Jamuria Police Station's Officer-in-Charge Soumendra Singh Thakur.
Another police officer said the temperature around the furnace shot up to several degrees Celsius after the blast, making rescue operations extremely difficult.
Locals claimed that eight to 10 workers were still unaccounted for and were feared trapped inside the factory. They also said that the houses near the factory developed cracks under the impact of the explosion.
Questioning the safety standards at the plant, local BJP leader Deep Bandopadhyay alleged that no representative of the factory management or even security personnel was present after the accident.
"Despite such a devastating incident, nobody from the management was seen at the spot. Local MLA Bijan Mukhopadhyay immediately arranged the ambulances to ensure the injured were taken to hospitals without delay," Bandopadhyay said.
He further alleged that workers at the factory were forced to labour under unsafe conditions and demanded a comprehensive probe into the incident.
(With inputs from PTI)