The US Food and Drug Administration (FDA) on Friday warned consumers not to use a brand of weight loss pills that claim to be "100 percent herbal" after lab tests showed they contain a dangerous stimulant.

FDA laboratory tests found that Slimming Beauty Bitter Orange Slimming Capsules contain "excessive amounts of sibutramine," a stimulant which is supposed to be available only on prescription and which could cause high blood pressure, stroke or heart attack in some consumers.