Banners signed by a cult-like Mexican drug gang say that cartel members launched firebombing attacks on a PepsiCo. subsidiary because they believe the snack company let law-enforcement agents use its trucks for surveillance.

Five Sabritas warehouses and vehicle lots were attacked Friday and Saturday in the Mexican states of Michoacan and Guanajuato. Officials say four alleged members of the Knights Templar cartel have been detained in the case, which they link to extortion. At least 10 banners hung around the city of Apatzingan on Thursday accuse Sabritas of ferrying government agents.

The company denies that allegation, which was also circulated in emails before the attacks. Mexican drug cartels frequently earn money by demanding protection payments from small businesses. They previously had never systematically targeted a transnational firm with such attacks.