Kanpur | Four workers were found dead inside their rented room in the Panki industrial area here on Thursday morning, with police suspecting carbon monoxide poisoning caused by burning coal in a room overnight, an official said.

Panki Assistant Commissioner of Police Shikhar said the deceased, identified as Arun Verma (32), Sanju Singh (22), Rahul Singh (23) and Daud Ansari (28), all residents of Deoria district, were employed at an oil seeds mill in Industrial Area Site-2.

Seven workers were staying at the site, but three had stepped out for the night. The remaining four cooked dinner and later lit a coal in a metal tray to keep warm as temperatures dipped below 10 °C, the officer said, adding that they locked the room from inside, unaware that it lacked ventilation.

When the men failed to wake up by morning, co-workers knocked repeatedly but received no response. Police were alerted, and the door was broken open in the presence of officers, revealing all four lying dead on the floor, they said.

The room was smoke-filled, and the coal and sawdust were still smouldering, police said.

The bodies were sent for post-mortem to confirm the exact cause of death, police added.

Nagendra, a co-worker staying in the adjacent room, raised the alarm around 6 am when attempts to wake them up failed. Arun's brother Amit, who lives nearby, rushed to the site and assisted police in opening the door.

The workers were part of an under-construction refinery project reportedly owned by Tarun and being developed by Indore-based Aditya Enterprises. A large stock of coal had recently been brought in for boiler testing. Police have since sealed the premises.

Commissioner of Police Raghubir Lal, who inspected the site, said the burning coal produced carbon monoxide that slowly filled the room. "They lost consciousness while asleep. By the time help arrived, all four had died," he said.

Forensic teams have examined the room, and Deputy Commissioner of Police (West) Dinesh Tripathi also inspected the spot and issued necessary directions to police personnel and experts.

The area has been secured, and an investigation into all aspects of the incident is underway, police said.