CORDOBA, Mexico -- In the lower-middle-class neighborhood of Las Estaciones sits a factory for making pesticides with parathion, among the deadliest nerve agents in the world.
The factory also makes herbicides with paraquat, a chemical so toxic that Finland, Sweden and the Netherlands have banned it. There is no known antidote. Paraquat is particularly harmful to the lungs.
Within 200 yards of the Agricultura Nacional plant are a day-care center, a grade school, a special education school, a public market, two churches, two health clinics and scores of private homes.
Since February, residents had noticed strange smells periodically coming from the 50-year-old structure, which previously had been used as a chemical warehouse. Many people, including the headmistress of the grade school, complained of headaches and nausea.
In March, about 40 residents signed a letter to Mexico's environmental agency asking that the plant be closed. But nothing came of it, even though the agency later acknowledged that the building was licensed only to store chemicals, not to make them.
"It was like writing to Santa Claus," said Juan Molino Velasquez, a truck driver who owns a radio-equipped ambulance that is part of an amateur rescue service.
On May 3, it was Mr. Molino Velasquez who radioed Cordoba's Red Cross headquarters.
The pesticide factory was on fire after a series of small explosions. Within a few minutes, people were vomiting in the streets.
The ensuing panic produced a Dunkirk-style evacuation in which more than 2,000 people were carted off in taxicabs, trucks, buses, private cars and ambulances. The neighborhood was sealed off for two days.
The fire and explosions scattered or burned 4,752 gallons of parathion, 2,112 gallons of paraquat, 792 gallons of the common herbicide 2,4-D and 396 gallons of pentachlorophenol, a wood preservative that contains dioxin, according to a preliminary study by the Mexican Association of Fertilizer and Pest Control Industries.
The study found that about 15 percent of the chemicals escaped from the plant, apparently dispersed by the blaze, explosions or water from fire hoses. The rest were confined to the factory building.
An association spokesman would not confirm the report.
The most deadly of the chemicals was parathion, a substance so dangerous that the Environmental Protection Agency has recommended that it be banned in the United States. A single drop of pure parathion in the eye is fatal, studies show.
Although no one died in the Cordoba disaster, the accident represents to many critics the limits and risks of Mexico's infant environmental protection system.
Indeed, many U.S. ecologists fear that a proposed free-trade agreement with Mexico would permit an influx of U.S. chemical companies seeking to take advantage of Mexico's low wages and limited enforcement of environmental laws.
In 1988, Mexico adopted a strict environmental law. But the environmental agency in this nation of 81 million people has only 210 inspectors -- almost exactly the number in Maryland, which has a population of 5 million.
Nearly half the Mexican inspectors are concentrated in Mexico City or along the U.S. border. For provincial places such as Cordoba, a city of 150,000 about 140 miles east of the capital, the inspections are few and far between.
Among other things, the Cordoba disaster revealed that:
* The pesticide factory was operating illegally in the heart of a residential district. Many residents, and Alfonso Cipres Villareal, the head of a Mexico City environmental group, charge that the owners must have paid off government officials. The charge is heatedly denied by the authorities. Two of the company's principals could not be reached for comment after a week of telephoning.
* The factory's management was permitted to remove files and some of the remaining chemicals in the early-morning hours after the fire.
"They were allowed to take away the incriminating evidence," said Dr. Ernesto Saul Vargas, a dentist who watched from his house across the street. Two plant managers and an employee were later charged with violating an environmental law.
* The federal environmental agency did not respond to residents' complaints before the accident. Federico Sanchez, a local agency representative, later denied that there had been any serious damage.
The Red Cross reported that more than 200 people were poisoned. Some were given atropine, a powerful chemical used to combat nerve agent poisoning.
* Firefighters clearly did not know how to fight the fire.
Rod Turpin, an EPA pesticide expert, said that using water to smother a parathion fire could have produced even deadlier chemicals, such as phosgene, a nerve agent used in gas warfare. The preferred method is to let the fire burn out, since higher temperatures destroy toxicity, he said.