London (CNN Business) Nestle will tighten quality controls on the coffee beans it buys, after tests flagged levels of the controversial weedkiller glyphosate that were close to regulatory limits.

The world's largest coffee company said in a statement Friday that it had found glyphosate residues close to the maximum allowed in some deliveries of green coffee beans.

Glyphosate is the key ingredient in Monsanto's weedkiller, Roundup. In the United States, juries have awarded huge monetary damages to people who say their cancer was caused by exposure to glyphosate. Bayer, which owns Monsanto, says the herbicide is safe when used properly, as does the US Environmental Protection Agency.

Neumann Kaffee Gruppe (NKG), one of the world's largest traders, said glyphosate was one of a number of substances it monitored on the coffee it buys. Nestle buys some of its coffee beans from NKG. It was too early to say what consequences Nestle's tighter controls would have on NKG, a spokesperson said.

Nestle's NSRGF decision to increase the frequency of checks was unlikely to disrupt global coffee supply chains, a spokesperson said. "This is not a new process, we are just reinforcing controls," the spokesperson told CNN Business. Tests were done before the coffee was shipped from the countries of origin.

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