At least four workers died and six others fell ill after inhaling toxic gas that leaked at the coal chemical unit of Rourkela Steel Plant in Odisha on Wednesday, The Indian Express reported, quoting officials. The workers were engaged in maintenance work at the unit when the incident took place, a police official said, adding that further investigations into the matter were underway.

The deceased have been identified as Ganesh Chandra Paila (59), Abhimanyu Sahu (33), Rabindra Sahu (59), and Brahmananda Panda (51), PTI reported.

Archana Satpathy, public relations officer of the Rourkela Steel Plant, said all the four worked for a maintenance contractor firm Star Construction, according to the Hindustan Times.

The workers fell sick around 9.45 am on Wednesday morning, following which they were admitted at the local Ispat General Hospital. Four of them died while undergoing treatment, according to The Indian Express.

Unidentified officials said that the coal chemical department in the plant produces coke oven gas, reported the Hindustan Times. An inquiry into the cause of the leak and lack of safety protocols at the site will be initiated, the officials said.

Odisha Chief Minister Naveen Patnaik expressed grief at the deaths and wished speedy recovery of those hospitalised.