At least nine people died and 19 were injured when a boiler in a chemical factory in Dhaulana area of Uttar Pradesh’s Hapur district exploded at 3.30pm on Saturday.

Praveen Kumar, inspector-general of police of the Meerut range, said: “The factory, located in the industrial area, is authorised to make electronic goods but they were making chemicals.”

“The rescue operation is going on. The injured have been sent to hospital. Some of them are in critical condition,” Kumar said on Saturday afternoon.

District magistrate of Hapur Medha Roopam said: “While the factory was meant for manufacturing electronic items, something else was going on there. An inquiry will reveal everything.”

There was a board of the Krishna Organics Company put up outside the chemical factory, where the boiler explosion took place.

Eyewitnesses said the impact of the explosion was so intense that tin-shed roofs of many neighbouring factories went flying.

An employee of the factory, who was engaged in the rescue operation, was quoted by the local media as saying: “There were about 60 labourers in the factory after lunch time when the boiler exploded. We had brought out nine dead and 19 injured only till 7pm. We don’t know about others. Many injured may not be able to survive. The death toll may go up.”

The industrial area is developed by the industries department of the Uttar Pradesh government. The same department is also supposed to monitor the activities of the private industries of the state.

Chief minister Yogi Adityanath has expressed sorrow over the death of the workers.

Prime Minister Narendra Modi tweeted: “The incident in the chemical factory of Hapur in Uttar Pradesh is heartrending. I express my condolence to the families whose members have lost their lives. The state government is promptly engaged in treatment of the injured and other assistance.”