Chennai: The death toll in the boiler blast at Neyveli Lignite Corporation (NLC) that took place last week rose to 13 on Wednesday, an official from the company confirmed to ET. The official went on to add that three workers have been discharged and seven are still in hospital.The mishap took place last Wednesday six men were killed and 17 others injured when a boiler exploded at NLC's thermal plant in Tamil Nadu's Cuddalore district.The mishap occurred around 9:45 am at the fifth unit of the thermal power station-II. According to a statement from the company, thermal power station II (TPS-II) was under shut down and maintenance activities were being carried on but a fire broke out in the boiler area subsequent to an explosion, resulting in injuries to the NLC maintenance team comprising one executive, two supervisors, three non-executive employees and 17 contract workmen.This is the second such instance in a span of a few months of a boiler explosion at this plant. On May 7, eight people were injured in a boiler blast at the same plant. "Out of the 23 injured, six workmen belonging to a contractor succumbed to injuries on the spot. All the 17 injured were immediately rushed to NLCIL Hospital, 16 of them after initial treatment were immediately sent to Apollo hospitals in Chennai for further super specialty treatment and one with minor injuries is being treated in NLCIL Hospital," the statement from the company on July 1 read.The company added that a high-level enquiry headed by PK Mohapatra, retired director (technical), NTPC had been ordered into the cause of the accident apart from an internal enquiry committee with senior executives headed by Director (Power) of NLCIL."The Unit Head of TPS-II has been placed under suspension pending enquiry by the management. All the four units of 210 MV each of TPS-II Stage II have been ordered for shut down for immediate safety audit," the company had said.