SAO PAULO–Biotechnology firm Monsanto Co. (MON) said Wednesday it has "temporarily" stopped charging Brazilian farmers royalty fees for the use of its Roundup Ready soybean seeds, amid legal proceedings in the country's top grains-producing state.

In a class-action lawsuit, the Mato Grosso state agriculture federation, Famato, and other local farming groups secured a court injunction last week against royalty charges by Monsanto for Roundup Ready soybean seeds and Bollgard I cotton seeds. They argued that Monsanto's patent on the seeds–which are genetically modified to resist herbicides and pests, respectively–expired two years ago in Brazil.

Monsanto said in a statement Wednesday that it is appealing the court's decision in order to resume royalty charges, and that it expects the injunction to be overturned "in the coming weeks." But although the court order only applies to Mato Grosso, Brazil's top soybean-growing state, Monsanto added that it has "voluntarily suspended royalties charges" in all of Brazil.

The company disputed the farming groups' claim that the patent for Roundup Ready soybean seeds expired in 2010, saying it has intellectual-property rights on the technology until 2014. As for Bollgard I cotton seeds, the company said it hasn't charged royalties since its patent expired in 2011.

Famato said the lawsuit was based on a "technical and legal study" it commissioned along with Mato Grosso state soybean growers association Aprosoja that showed the patents for both seeds expired Sept. 1, 2010.

Famato President Rui Prado attributed the discrepancy between the dates in its filing and those provided by Monsanto to "the lack of transparency" on the part of the company.

"They get one patent after another, even for seeds they don't sell commercially. That creates confusion", Mr. Prado said, adding that Monsanto doesn't list its patent numbers on customer receipts or the bags of seeds being sold. "We've asked them what patent they were charging us for, and they didn't answer".

In addition to the injunction, the farmers' lawsuit also seeks reimbursement for up to double the 300 million reais ($147.4 million) in royalties collected by Monsanto since its patents allegedly expired, Mr. Prado said.

Farmers usually pay royalties to Monsanto via an invoice included in seed purchases, he said. The multinational trading companies that buy and export soybeans in Brazil also have agreements with Monsanto to test for transgenic soybeans, allowing them to deduct a small percentage of the soybeans in a shipment from farmers who haven´t paid the invoice.

Brazilian soybean farmers such as Mr. Prado are planting what will likely be a record crop next year, with Conab, the government food-supply agency, forecasting production at between 80.1 million and 82.8 million metric tons. Mato Grosso accounts for almost 30% of Brazil's soybean production.