Meanwhile, Gujarat Pollution Control Board Regional Officer J B Parel informed Shah today that the gas had been identified as methyl mercapton, a foul-smelling gas added to odourless liquefied petroleum gas for detection purposes.

However, GPCB test teams did not find any evidence that the gas was leaking from the plants of any of the heavyweight plants of the GGCL, the ONGC, Reliance Industries, GSPCL, GAIL and Essar. ONGC and GGCL, however, are known to use methyl mercapton on a large scale.

That was partly the reason why the two companies had been asked to attend Wednesday's meeting, Shah said. ``I have also issued orders to officials of the Bharuch-based Birla Cellosic to attend the meeting as the residents of the city are being affected'', he added.

In addition, all companies have been asked to check their pipelines, fittings and storage facilities.

Gas leaks became a major issue after a brief respite when a large number of residents in the Katargam, Ashwini Kumar, Varachha, Dabholi and Singanpore areas complained of a foul smell gas after sunset on Sunday.

``Steady progress is being made in the matter though we still haven't identified the precise source of the gas'', Shah said when asked why the administration still hadn't declared who was releasing the gas.