The FDA has listed more than 25 weight loss products to avoid because they contain ingredients that are not labeled and could cause serious health problems such as high blood pressure, seizures, heart attacks, or strokes.

Most of the diet pills appear to be coming from China, and are mainly sold on the internet, the AP reports. The FDA said it may take action, such as issuing warning letters or seeking criminal charges on a number of companies linked to the sale of those products.