The warning letters explain that "no hormones" and "hormone free" are false claims because all milk contains naturally occurring hormones, and milk can not be processed in a manner that renders it free of hormones. FDA also cautioned the firms that the agency could pursue further action such as seizure and/or injunction, if they fail to take prompt action to correct their labels. FDA said that food manufacturers who do not use milk from cows treated with recombinant bovine somatotropin (rbST) may voluntarily inform consumers of this fact on their product labels or labeling, provided that the statements are truthful and not misleading.