Popular burrito chain Chipotle Mexican Grill Inc’s claims of using no genetically modified ingredients on its menu items has proven to be a hit with consumers, but not everyone is happy.

Last week, Kaplan Fox & Kilsheimer LLP filed a federal class action law suit against Chipotle on behalf of California consumers who food from the restaurant since April 27. The lawsuit alleges Chipotle's marketing and advertising campaign that claims its menu does not contain genetically modified organisms (GMOs) is deceiving and misleads consumers because they say many of the menu items actually do contain GMOs.

Specifically, the complaint alleges that Chipotle has marketed its "Food With Integrity" brand to healthy-lifestyle and environmentally conscious consumers who are willing to pay premium prices for food that aligns with the consumers' ethical eating choices. The complaint alleges that Chipotle's claims are false and misleading to customers because Chipotle's menu was never free of GMOs at any time. Among other things, the complaint alleges that Chipotle serves meat products that come from animals which feed on GMOs, including soy and corn, and that Chipotle sells soft drinks that are made with corn syrup.

According to Reuters, Chipotle declined to comment on the allegations, but said the company does plan to contest the lawsuit.

On its website, Chipotle does include disclaimers that its soft drinks are made with corn syrup which is almost always made from GMO corn. The company also acknowledges its meat and dairy products come from animals that are not genetically modified, though the feed those animals consume likely contains GMO ingredients.

 “We are working hard on this challenge, and have made substantial progress: for example, the 100 percent grass-fed beef served in many Chipotle restaurants was not fed GMO grain—or any grain, for that matter,” the company said. “This is an important start, but we recognize that sourcing meat and dairy exclusively from animals never fed GMOs would be a long-term project that would represent further progress in this area.”