Three labourers died after inhaling toxic gas while cleaning a sewage treatment plant of a local civic body in Maharashtra's Thane, police said on Thursday.
The dead men were daily wage labourers and had no formal training in sewage cleaning, police said. Police added that the labourers were hired by a civic contractor, but were not given any protection gear, like masks.
The incident took place on Wednesday when the labourers were cleaning a chocked valve in a chamber of the non-operational sewage treatment plant located in Thane's Mira Road.
Police said one of the labourers climbed down into the sewage treatment plant to clean it. He, however, felt suffocated and collapsed. When two other labourers went inside to check on him, they died after inhaling toxic gas.
The dead labourers were identified as Muzaffar Moulik (24), Rafique Mandal (50) and Mofjum (18).
Another labourer, 17, who also inhaled the toxic fumes, was admitted to a hospital where he was undergoing treatment, police said.
The bodies were sent to a local hospital for postmortem, the official said, adding that a probe was underway.