The number of people suing over illnesses they believe were caused by radiation releases from the Hanford Nuclear Reservation increased to a little over 2,000 this week.

Federal Judge William Fremming Nielsen in Spokane agreed to add about 250 downwinders to the suit against early Hanford contractors.

During World War II and the early years of the Cold War, radioactive iodine was released into the air during production of plutonium at Hanford for the nation's nuclear weapons program. The radioactive iodine drifted downwind and fell to the ground to be ingested by residents in fresh fruits, vegetables and milk from cows that grazed on contaminated grass.

The new plaintiffs in the 1991 case include people who have learned only recently about the lawsuit or who have recently developed a medical condition they believe is linked to the radiation releases, said Richard Eymann, a Spokane attorney. His firm represents 208 of the new plaintiffs.

When Nielsen took over the lawsuit in 2003, downwinder attorneys said there were a little over 3,500 claims. The contractors' attorneys estimated the number of plaintiffs to be at least 1,000 more.

The numbers dropped as plaintiffs with illnesses that could not be clearly linked with radiation or who likely had received slight or no exposure were moved to an inactive list. Nielsen did not close the suit to new plaintiffs, however.

Many of those filing suit have thyroid disease, including cancer. Radioactive iodine concentrates in the thyroid. The suit also includes people who have other cancers they believe were caused by radiation releases to the air or Columbia River.

In another development in the case, defense attorneys have asked to challenge Nielsen's ruling last month that downwinders will not have to prove early Hanford contractors were negligent to win their lawsuit. That leaves only whether radioactive releases caused plaintiffs' health problems to be decided at trial.

"There are lots of errors that we think mount up to (the need for) reconsideration of the court," said Kevin Van Wart, attorney for the defense.

The court should have held a full hearing on the matter, he said. He also said that contrary to what the judge wrote in his order, it was not clear in the 1940s that radioactive iodine could cause thyroid cancer.

Although Nielsen indicated he is not likely to change his ruling, he said he would allow defense attorneys to file a motion for reconsideration. To keep the case moving, Nielsen has ruled that motions cannot be filed without his approval.

A trial date for 11 bellwether plaintiffs has been set April 18. Nielsen hopes a jury decision on a few of the cases will give attorneys guidance to settle the remainder.