While the company has termed the deaths as an accident caused by asphyxiation that occurred on Saturday night, both the CPM and Trinamool Congress claimed that a gas leak caused the deaths and alleged callousness on part of the HPL.

The deceased are Pintu Pradhan (35), Gopal Das (34) and Zakir Hussain (36). District Magistrate S D Chhoten Lama said the bodies were retrieved from a chamber and have been sent for postmortem. We have interrogated the HPL authorities over the deaths, he added.

A case of unnatural deaths has been registered with the Durgachak police station.

The HPL authorities said the unit had been shut down since May 8 for maintenance, and the deceased workers had gone into the process vessel of the unit as part of the maintenance activity around 11.30 pm on Saturday.

“The deceased were unskilled labourers and entered the Naptha Cracking unit of the plant without mandatory work permits,” HPL spokesperson Alok Chattopadhyay told The Indian Express. “Had they been issued work permits, it would have been made clear to them that certain sections are off-limits. Safety norms would have been made clear to them. The contractor violated the safety norms,” he added.

HPL authorities are conducting an internal investigation on how the three workers managed to enter the process vessel without work permits, which have to be obtained from security officials. Chattopadhyay said 4,500 workers are engaged in the maintenance operation.

Haldia Development Authority chairman and former CPM MP from Tamluk Lakshman Seth has demanded Rs 5 kakh compensation for the deceased’s families.

Trinamool Congress’ Suvendu Adhikary, who defeated Seth in the recent Lok Sabha polls, has demanded compensation of Rs 10 lakh for each family. “The labourers died due to a gas leak. Jobs should be given to their relatives and security measures should be reviewed at all industrial units. The CPM-backed union at HPL is corrupt,” Adhikari said.

HPL is the main petrochemical company in the country’s eastern zone concentrating on the production of naptha-based petrochemical products.

HPL is a joint venture of the West Bengal Industrial Development Corporation, Chatterjee Petrochem (Mauritius) Co Ltd and the Tata Group of Companies.