The accident took place around 4 am local time in the industrial city of Surat in Gujarat state. Police and a fire officer said the workers were at the mill when some chemicals were thrown nearby.

Speaking to Reuters, Chief fire officer of Surat Municipal Corporation, Basant Pareek said, “Chemicals were being illegally discharged from a tanker into a rivulet close to the mill, which possibly reacted with another chemical in the water and created toxic gas,”

“The workers inhaled the gas and started feeling suffocation. When we reached the scene, the workers were found collapsed on the road in their attempt to escape.”

Six workers died while 23 were hospitalized, seven in critical condition and on ventilators, Pareek said. Officers are investigating but no arrests have been made so far, senior police official Sharad Singhal said.

“This was not an accidental gas leakage. Hazardous chemicals were being discharged when the incident took place,” he said.