PORTLAND — An attorney for dozens of construction workers who sued the Army said yesterday that the Army was negligent in its response to a "major medical emergency" at the Umatilla Chemical Depot.

The employees alleged they were poisoned by sarin gas while working near a chemical stockpile. The trial pitting the construction workers against the Army opened yesterday in U.S. District Court.

The workers were building an incinerator at the chemical depot near Hermiston, in northeastern Oregon, more than four years ago when they suddenly fell ill and staggered from the building gasping, coughing and vomiting. Many still suffer from symptoms they developed that day.

The incinerator will be used starting next year to destroy nearly 4,000 tons of weapons packed with sarin and VX nerve agent that are stored in 89 concrete bunkers. The bunkers, as well as sheds containing bulk mustard, are several hundred yards from the incinerator site.

The plaintiffs' attorney, James McCandlish, said during opening statements that the Army was wrong to have immediately ruled out chemical poisoning and was negligent for relying on its civilian contractor, Raytheon, to deal with the sick workers.

He also said the Army didn't react quickly enough to the medical emergency, thereby increasing the workers' chemical exposure and worsening its long-term effects.

McCandlish said the Army did not begin testing for chemical agents until three hours after the incident and then waited 90 minutes before testing the areas where the workers fell ill. Sarin can disperse in as little as 30 minutes, he said, making it impossible to discount chemical exposure.

"They ruled out chemical agents prior to even doing testing," McCandlish said. "No government employee went to the site and performed an evaluation of signs and symptoms."

McCandlish said the Army's on-site doctor relied instead on phone reports from Raytheon employees, who said they didn't need Army assistance.

"We believe that the Army's defense is hiding its collective head in the sand like an ostrich," McCandlish said.

Government attorneys, however, said the Army didn't intervene because it had immediately ruled out chemical agents.

Army employees had entered four bunkers that morning for routine checks and found no weapons leaking in any of those bunkers. That work concluded at least 35 minutes before any workers showed symptoms, said James Brennan, attorney with the U.S. Department of Justice.

Army employees working in street clothes next to the stockpile didn't show any symptoms, while construction workers did, he said.

"The Army, knowing what its operations were on that day, knew that this incident was a localized event at the construction site and not related to any chemical incident," Brennan said.

In addition, he said, Raytheon told Army personnel that it didn't need assistance and had ruled out sarin exposure.

The Army was under no obligation to send its doctor unless Raytheon requested help, he said. Nonchemical accidents at the incinerator site were to be handled by Raytheon as specified in pre-construction agreements, Brennan said.

Raytheon was dropped as a defendant after reaching an undisclosed settlement with the workers. The company now is called the Washington Demilitarization Group.

An extensive investigation by the Army, which owns the depot, and federal regulators never determined the cause of the men's symptoms. Possibilities listed by investigators included pepper spray, ammonia or fumes from the welding, grinding and other construction activity.

The first phase of the trial is to determine whether the Army was negligent. A second phase, would deal with damages.