Shares of Monsanto parent Bayer surged on Monday after the U.S. government put itself in the German company's corner, arguing that a ruling that found the pesticide Roundup caused cancer should be overturned.

In a friend of the court brief filed Friday with a San Francisco-based appeals court, the Environmental Protection Agency said it reviewed and approved the warning label on the weed-killing product, and that a jury finding based on California law should be reversed. The Department of Justice joined the EPA in weighing in on the only federal jury ruling thus far in a long-running saga over Roundup.

Over the summer, a U.S. district judge slashed to $25 million the amount to be awarded in the case of a man who claimed his non-Hodgkin's lymphoma had been caused by years of using Roundup. But the judge declined to reverse the jury finding that Roundup was defective because its label did not include a cancer warning. Monsanto maintains Roundup is safe.

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Roundup contains glyphosate, which is being tested in the courtroom and in America's homes amid concern about the chemical's safety. Tests from environmental groups have added to consumer worries, such as one study that found 21 oat-based cereal and snack products, including Cheerios, contain traces of glyphosate. The most widely used herbicide in U.S. agriculture, glyphosate is used by farmers and sprayed on golf courses and residential lawns to kill weeds.

The EPA in May said it "continues to find that there are no risks to public health when glyphosate is used in accordance with its current label and that glyphosate is not a carcinogen." But environmental and other advocates dispute that determination, which came four year after the World Health Organization termed glyphosate as "probably carcinogenic to humans."

Bayer acquired Monsanto for about $63 billion in 2018, along with tens of thousands of lawsuits over Roundup. The company has lost three trials in which people alleged that Roundup caused them to get cancer. Bayer has appealed the verdicts, but this month said it agreed to delay two Roundup-related trials pending in the U.S. to allow for a possible settlement.

Bayer found reason for cheer in the latest legal turn, saying in an email that the company is "encouraged" that the U.S. government and other parties opted to offer legal views in support on the company's appeal. "The number and stature of these parties speaks clearly to the importance of the issues in dispute in this case to a diversity of interests including governments, health care providers, farmers and manufacturers," a Bayer spokesperson stated.

The company also found support on Wall Street, with its stock at one point rising to 14-month highs of $73.93, a gain of 3.5%.