A contract worker was killed and a private security guard severely injured following an explosion at the seventh unit of the state-run Durgapur Projects Limited (DPL) on Tuesday morning.

Police said when the explosion occurred, Omprakash Chowhan, 38, was carrying out a cleaning job at the unit that was closed on Tuesday.

Omprakash died on the spot, while private security guard Bam Ruidas, 39, was injured. Doctors said Bam’s right leg had blown off.

The incident occurred around 11am when the power utility had shut down generation because of inadequate water in the wake of the Durgapur Barrage crisis.

Initially, the DPL management said the explosion had been triggered by a short-circuit at the power generating unit.

But the engineers of the power utility ruled out any such snag.

Trade unions INTUC and Citu and Trinamul Congress have demanded proper investigation into the incident.

“The incident is very serious and shocking. If there were no electrical fault what was the reason behind the blast. We demand investigations,” said Biswanath Padial, Trinamul trade union president in West Burdwan and MLA.

Police have reached the spot and started investigations. The police suspect chemicals used in cleaning led to the blast.

“The chemical was in an empty drum that was handled by the deceased during cleaning work. We have asked forensic experts to find out what was the chemical,” said a senior police officer.