In charge chief fire and security officer G M Kothwala said on Sunday that though the fire brigade had been trying to find out the exact source of the mysterious gas, they had not been successful so far. ``Anyway, the intensity of the gas was much less today in comparison to yesterday'', he said.

The collector, meanwhile, has called a meeting on Monday to discuss the progress made in the inquiry into the incident. Listing the probable causes, Kothwala said the gas could have escaped from a leaking tanker or released by a chemical company when the pressure in its containers got too much. The gas could also be remnants in chemical tins sold as waste, he added.

People had complained the gas irritated the eyes and caused uneasiness when inhaled, though no one has been seriously affected. Kothwala said, ``Though the gas is not fatal, it does irritate the eyes and poses general health hazards''.

He would submit his report on the three possible sources of the gas to Shah on Monday, Kothwala said, adding that because of the low density, there was no way to identify the gas.

Incidentally, the episode bears echoes of a two-year-old incident, when a similar unidentified gas had been traced to partially filled chemical containers sold off by units as scrap to a Navsari bazaar dealer. The civic authorities had then formulated a plan to identify and penalise such industries. However, the plan has remained on paper.

Among the steps Kotwala has suggested in his report are a ban on the movement of hazardous chemical tankers in the city, a ban preventing chemical industries from selling scrap to local dealers and surprise checks on chemical industries.