Hundreds of lawsuits against Monsanto Co by cancer survivors or families of those who died can proceed to trial, a federal judge ruled on Tuesday, finding there was sufficient evidence for a jury to hear the cases that blame the company’s glyphosate-containing weed-killer for the disease.

The decision by U.S. District Judge Vince Chhabria in San Francisco followed years of litigation and weeks of hearings about the controversial science surrounding the safety of the chemical glyphosate, the key ingredient in Monsanto’s top-selling weed-killer.

Monsanto is now a unit of Bayer AG (BAYGn.DE), following a $62.5 billion takeover of the U.S. seed major which closed in June.

The U.S. Environmental Protection Agency last September concluded glyphosate is likely not carcinogenic to humans. But the World Health Organization in 2015 classified glyphosate as “probably carcinogenic to humans.”

Chhabria called the plaintiffs’ expert opinions “shaky” and entirely excluded the opinions of two scientists.