By Brendan Pierson and Dietrich Knauth

(Reuters) -A Washington jury on Tuesday ordered Bayer to pay $100 million to four people who say they were sickened by toxic chemicals known as PCBs at a Seattle-area school, but found the company was not liable for injuries alleged by 11 others.

The verdict, which follows a two-month trial, is the latest in a string of trials against the chemical company over the alleged contamination at the Sky Valley Education Center in Monroe, Washington.

More than 200 students, employees and parents have said they developed cancer, thyroid conditions, neurological injuries and other health problems from polychlorinated biphenyls, or PCBs, leaking from the school's light fixtures. The chemicals were made by Monsanto, which Bayer acquired in 2018.

Monsanto said in a statement it will pursue post-trial motions, and an appeal if necessary, to overturn the verdict or reduce the "excessive" damages awarded to the four plaintiffs.

Evidence at trial showed low to non-existent level of PCBs, which could not have caused the injuries alleged, Monsanto said.

The jury concluded that Monsanto intentionally concealed information about PCBs. It awarded $25 million in compensatory damages and $75 million in punitive damages.

"Every case is different and the juries are clearly working very hard to try to get things right for the generational harm caused by PCBs," said Henry Jones, an attorney for the plaintiffs.

Verdicts in previous trials over the alleged contamination at the school, which have involved different groups of plaintiffs, have totaled more than $1.5 billion, though some have been reduced or overturned. The remaining judgments are also the subject of appeals, Monsanto said.

Last year, a verdict for $185 million in favor of three teachers and a teacher's spouse was overturned on appeal in favor of Monsanto on multiple grounds.

The state appeals court agreed with Bayer that the trial court wrongly applied the laws of Missouri, where Monsanto was based, allowing the claims to be filed decades after the company stopped producing PCBs in 1977. The company said Washington law should apply instead, and it would block the plaintiffs' claims as filed too late.

Washington's highest court is expected to hear an appeal of that ruling.

In August, an $857 million verdict was slashed to $438 million, after a judge found it included excessive punitive damages.

Bayer acquired Monsanto for $63 billion in 2018. Since then, lawsuits over PCBs, and more significantly over claims that the weedkiller Roundup caused cancer, have weighed heavily on the company's shares.

PCBs were once used widely to insulate electrical equipment, and were also used in such products as carbonless copy paper, caulking, floor finish and paint. They were outlawed by the U.S. government in 1979 after being linked to cancer and other health problems. Monsanto produced PCBs from 1935 to 1977.

Plaintiffs have said Monsanto knew of the dangers of PCBs for decades, but concealed them from the public and from government regulators.

Bayer has argued plaintiffs have failed to prove their injuries were caused by PCBs, and that the levels found in the school were deemed safe by the Environmental Protection Agency. It has also said the school ignored warnings from government officials that the light fixtures in the aging building needed to be retrofitted.

(Reporting By Brendan Pierson and Dietrich Knauth in New York; Editing by Alexia Garamfalvi, Lisa Shumaker, Lincoln Feast and Christian Schmollinger)