"Official warning" is a phrase used to describe a formal notice or a serious alert given by someone in authority to inform you that you have done something wrong or violated a rule. Full definition
Health officials warn against eating fish caught in these waters, since mercury can cause birth defects, brain damage and other ailments. (treehugger.com)
All three of the exchanges have issued official warnings regarding the halt on margin trading. (bitcoinist.com)
Officials warned of the dangers of triggering market moves that could negatively influence inflation. (cnbc.com)