Assistant commissioner of police, Rajesh Pathak said: “The nature of the gas is still a mystery. We have asked Gujarat Pollution Control Board to submit their report at the earliest but there is no intimation from the agency yet. GPCB collected samples from the drain in Narol. We have begun hunting for chemical factories which may have dumped effluents illegally, causing the gas emission from the sewer. Without this GPCB report, we cannot proceed against people responsible for this.”

“The preliminary postmortem report says that the victims died of suffocation caused by gas. The gas was heavier than air and affected those sleeping on the floor.