PITTSBURGH (AP) _ When cancer victims and their families won $36.5 million in a trial against uranium plant operators, their lawyers called it the biggest verdict involving radiation exposure in the country.

Now, they have to try it all over again.

U.S. District Judge Donetta Ambrose on Tuesday ordered a new trial, ruling that some testimony was prejudicial and evidence was improperly withheld from lawyers for the companies.

Residents of Apollo, about 25 miles northeast of Pittsburgh, say they inhaled white radioactive dust from the plant for three decades. The dust contained uranium that caused an unusually high cancer rate, they claimed.

The plant shut down in 1986, and residents sued in 1994.

Attorneys for plant operators Atlantic Richfield Co. and Babcock and Wilcox Co. argued that no one could prove a medical link between radiation and the cancers.

A jury disagreed last September and ordered the companies to pay $36.5 million in damages.

Ambrose said evidence including testimony from scientists who linked violations of federal emissions standards to the cancers was ``highly prejudicial and often irrelevant.''

Ambrose, who presided over the original trial, said she agreed with arguments from company attorneys that no juror could ``remain unaffected by that evidence.''

The judge also said scientific evidence obtained by the families should have been shared with the companies.

``We tried it the first time and we won, and we'll try it the second time and we'll win,'' said Fred Baron, attorney for the families.