Sheer negligence on part of the NTPC Unchahar plant in Rae Bareli was the reason behind the explosion at the thermal power plant, according to an investigation carried out by the Uttar Pradesh labour department, Hindustan Times reported on Friday. The toll in the explosion, one of the country’s worst industrial accidents in years, rose to 32 on Friday, PTI reported. More than 100 people have been injured.

The five-member team found that clinkers were formed in the boiler duct from stone-like residue from the burning of coal. The staff at the power plant did not clear the clinkers which is believed to be the main reason behind the explosion, the probe team said.

“Formation of clinkers from the burning of coal is not an unusual phenomena, but it is poked and hammered manually into small pieces for removal from the boilers at regular intervals,” Deputy Director, Labour, Jagmohan told the newspaper. He said the operating staff, however, did not clear the clinkers, “allowing the deposit to accumulate that choked the space for fluid gas to come out”.

NTPC, formerly known as the National Power Thermal Corporation, has formed a three-member committee to investigate whether safety norms were violated and what caused the blast. The National Human Rights Commission had asked for a report on accident.