New Delhi: An explosion of hot gas at a boiler at NTPC Ltd’s Unchahar power plant last year that killed 45 workers was the result of an “error in judgement" by some of the plant’s most experienced operators, according to an internal report on the state-run electricity producer’s biggest disaster.

The plant’s head of operations, head of ash handling maintenance and head of boiler maintenance—each with 28 years of experience—made a decision not to shut down a 500-megawatt (MW) boiler at Unchahar to clear a buildup of ash prior to an overpressurization in the unit that caused the gas release, said a summary of the report reviewed by Reuters.

“The shutdown of the boiler much before the incident would have been prudent," the report, prepared by an internal committee of NTPC, said. It was not clear from the summary when the report was submitted.

NTPC declined to release the full report or comment on the lapses mentioned in it. The company has revised its safety policy and is regularly conducting safety audits and mock drills, a spokeswoman said in an email to Reuters.

A spokesman for Bharat Heavy Electricals Ltd which made the boiler tubes at Unchahar did not respond to calls and emails.