Major agribusiness company Monsanto has filed a lawsuit in California to prevent glyphosate from being added to the US state’s list of known carcinogens, according to a Reuters news agency report. Glyphosate is the main ingredient in Monsanto’s Roundup herbicide.

The suit has been filed against the state’s Office of Environmental Health Hazard Assessment (OEHHA) and the agency’s acting director, Lauren Zeise.

OEHHA said last September that it planned to add glyphosate to the list after the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC) classified it as a probable carcinogen in March last year.

However, the OEHHA decision has been disputed by Monsanto which cites decades of studies showing glyphosate is safe, including a 2007 study by OEHHA that concluded the chemical was unlikely to cause cancer. The company stated that the IARC classification is inconsistent with the findings of regulatory bodies in the US and around the world.

Nevertheless, Monsanto is now being sued by farmworkers who claim that Roundup has caused their cancers. The first US suit was filed last September in Los Angeles.

However, by contrast, the European Food Safety Authority (EFSA) said in November 2015 that the herbicide ingredient was unlikely to pose a carcinogenic hazard to humans.

Earlier this month, EFSA’s executive director Bernard Uhl published an 18-page response to criticism of his team’s assessment. He said IARC’s first screening assessment “should not be compared with the more comprehensive assessment done by authorities such as EFSA which are designed to support the regulatory process in close cooperation with the member states in the EU.”

Roundup is used by farmers all over the world, generating revenue of $4.8 billion for Monsanto in fiscal 2015.