Indian scientists resumed operations at the Union Carbide plant in Bhopal today to dispose of the remaining poisonous gas.

In anticipation of that five-day process, Indian scientists yesterday described the chances of another accidental discharge as "very low." They added that the risk will progressively decrease as the work continues.

The operation started at 10:18 a.m. local time in the presence of Madhya Pradesh Chief Minister Arjun Singh. A small flame at the top of the plant signaled the operation was underway, 13 days after the pesticide factory spewed out tons of the deadly gas that spread over densely populated slum neighborhoods, killing more than 2,000 persons and sickening 150,000 others.

S. Varadarajan, director general of the Council of Scientific and Industrial Research, who is supervising the process, said that American and Indian experts were prepared for any "unanticipated reaction" of the remaining 15 tons of methyl isocyanate.

At a news conference in Bhopal yesterday, Varadarajan said the process would begin with dissolution of alpha naphtha in a carbon tetrachloride solution in the presence of catalysts and that the methyl isocyanate would be added slowly, producing heat and the pesticide marketed by Union Carbide under the brand name Sevin.

The chief of the Indian task force said that the liquefied methyl isocyanate inside the storage tank was stable and there had been no rise in temperature that would cause a chemical reaction and subsequent buildup of pressure inside the tank. "We have designed a new containment system and augmented special measures for an unanticipated reaction," Varadarajan said, according to Indian news agencies.

In a rehearsal of the operation, an Indian Air Force helicopter yesterday sprayed water over the chemical plant, the critical part of which has been covered by a huge tarpaulin. Methyl isocyanate, when released in the atmosphere, is quickly neutralized as it comes into contact with water.

The vent scrubber through which the chemical will pass has been shrouded in a screen of jute sacking cloth, on which water hoses have been trained. Eight helicopters have been standing by to spray water on the plant.

But as the zero hour approached, residents continued to jam buses and trains leaving the city, despite entreaties by the authorities not to panic. Estimates of the number that had joined the exodus ranged from 100,000 to 250,000 out of a population of 800,000.

The United News of India reported from Bhopal that the city's principal bus depot had sold more than 60,000 tickets, and that trains were running up to 60 percent above their normal loads.