Bareilly: Three labourers died of suffocation while another fell unconscious during the cleaning of a tank at a unit of an agro firm here on Tuesday, a senior official said.
Additional District Magistrate (City) Ram Dulare Pandey said the incident took place at the Jauharpur unit of B L Agro.
When three of them did not come out for some time, another labourer was sent inside and he fell unconscious, the ADM said.
They were rushed to the SRMS Medical College hospital, where the doctors declared Vijay (32), Neeraj (22) and Yasin (26) dead after a medical-examination.
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The condition of the fourth worker is critical, he said.
Investigation is on to ascertain if the incident occurred due to some poisonous gas, the ADM said.
On the orders of the district magistrate, a team of officers has been sent to the spot for detailed investigation, he added.