According to the complaint, Chipotle’s meat, cheese, and sour cream is made from animals fed with GMO soy and corn, and the soft drinks it serves are made with corn syrup made from GMO corn. The lawsuit was filed in the Northern District of California on behalf of California consumers who have purchased food from Chipotle since April 27, the day the company announced that it was “G-M-Over it.” Kaplan, Fox, and Kilsheimer filed the lawsuit.

The law firm issued a statement attributed to attorney Laurence D. King that read in part: “Chipotle’s advertising in its stores should have accurately informed customers about the source and quality of its ingredients and should not mislead consumers that they are serving food without GMOs when in fact they are.”

When reached for comment, King wrote in an email that beyond the complaint, “we have no comment at this time; rather we will let the complaint’s allegations speak for themselves.”

Chipotle is similarly mum. Chris Arnold, the company’s communications director, said only: “Generally speaking, we do not discuss details of pending legal action, though we do plan to contest this.” [Update, September 1, 2:30 pm: After this article was published, Arnold, Chipotle’s communications director, contacted Fortune to comment further. The lawsuit is “meritless,” and “filled with inaccuracies,” he said in an email. “Chipotle has always been honest and transparent with its customers, and the messaging surrounding our use of non-GMO ingredients is no exception.” Arnold said some of the graphics included in the complaint weren’t created or approved by Chipotle, including one depicting a menu board with all the letters “G” “M,” and “O” removed. The billboard indicating that “all” of Chipotle’s food was “non-GMO” also wasn’t created by Chipotle, he said, though he defended the language. He said that while the meat Chipotle serves is from animals fed GMO grains, “that does not mean that our meat is GMO, any more than people would be genetically modified if they ate GMO grains.” Also, Arnold said, the billboard is accurate because beverages aren’t “food.”]

In news reports at the time of the announcement, the company made clear that some of its ingredients are still made with GMOs. And at the bottom of the company’s Web page devoted to the topic is this disclaimer:

“The meat and dairy products we buy come from animals that are not genetically modified. But it is important to note that most animal feed in the U.S. is genetically modified, which means that the meat and dairy served at Chipotle are likely to come from animals given at least some GMO feed. We are working hard on this challenge, and have made substantial progress: for example, the 100% grass-fed beef served in many Chipotle restaurants was not fed GMO grain—or any grain, for that matter.

“Many of the beverages sold in our restaurants contain genetically modified ingredients, including those containing high fructose corn syrup, which is almost always made from GMO corn.”

The class-action complaint includes several examples of Chipotle advertisements that seem pretty explicit. “Now, all of our food is non-GMO” is the wording on one billboard, according to the suit. A photo in the complaint depicts a restaurant menu sign that reads, “Only non-GMO ingredients.” The named plaintiff in the lawsuit, Colleen Gallagher of Piedmont, Calif., could not be reached for comment.

Consumers, especially Millennial consumers, have expressed concerns about eating foods with GMO. But more than 90% of corn and soybeans grown in this country came from GMO strains in 2014, according to data from the USDA National Agricultural Statistics Service. Many scientists say the crops are safe, but critics say they could cause environmental problems and even cause harm to human health.

Chipotle has 1,831 restaurants globally. At the time of its announcement, Co-CEO and founder Steve Ells said the chain had decided to eliminate these GMO ingredients until the science is more definitive.