PORTLAND — A jury on Friday ordered an American military contractor to pay $85 million after finding it guilty of negligence for illnesses suffered by a dozen Oregon soldiers who guarded an oilfield water plant during the Iraq war.

After a three-week trial, the jury deliberated for just two days before reaching a decision against the contractor, Kellogg Brown and Root.

The suit was the first concerning soldiers’ exposure to a toxin at a water plant in southern Iraq. The soldiers said they suffer from respiratory ailments after their exposure to sodium dichromate, and they fear that a carcinogen the toxin contains, hexavalent chromium, could cause cancer later in life.

Rocky Bixby, the soldier whose name appeared on the suit, said the verdict should reflect a punishment for the company’s neglect of U.S. soldiers. “This was about showing that they cannot get away with treating soldiers like that. It should show them what they did was wrong, prove what they did was wrong and punish them for what they did.”

Each soldier received $850,000 in noneconomic damages and $6.25 million in punitive damages. Another suit from Oregon National Guardsmen is on hold while the Portland trial plays out. There are also suits pending in Texas involving soldiers from Texas, Indiana and West Virginia.

KBR was found guilty of negligence but not a secondary claim of fraud. U.S. District Judge Paul Papak acknowledged before the trial began that, whatever the verdict, the losing side was likely to appeal.

The company will appeal the verdict, said KBR attorney Geoffrey Harrison in a statement issued late Friday afternoon. Harrison said the verdict “bears no rational relationship to the evidence.” KBR witnesses testified that the soldiers’ maladies were a result of the desert air and pre-existing conditions. The contractor’s defense ultimately rested on the fact that they informed the U.S. Army of the risks of exposure to sodium dichromate.

KBR was tasked with reconstructing the decrepit, scavenged plant just after the March 2003 invasion while National Guardsmen defended the area. Bags of unguarded sodium dichromate — a corrosive substance used to keep pipes at the water plant free of rust — were ripped open, allowing the substance to spread across the plant an into the air.

Attorneys for the 12 Oregon Guardsmen focused on the months of April, May and June 2003, alleging KBR knew about the presence of sodium dichromate and took no action.

One of the soldiers’ key witnesses, a doctor, testified that the toxin caused a change to soldiers’ genes, leaving them more susceptible to cancer.

During the Iraq war, KBR was the engineering and construction arm of Halliburton, the biggest U.S. contractor during the conflict. KBR split from Halliburton in April 2007.