In a public statement posted on its website, the U.S. Food and Drug Administration said that Botox and Botox Cosmetic (Botulinum toxin Type A) and Myobloc (Botulinum toxin Type B) have been linked in some cases to adverse reactions, including respiratory failure and death, following treatment of a variety of conditions using a wide range of doses.

Botox became famous for smoothing facial wrinkles but it was also approved for medical uses such as treating cervical dystonia or rigid neck muscle. Myobloc is approved only for neck condition. An injection made with forms of the botulinum toxin block nerve impulses to muscles and makes them relax. The substance is also used off-label to stop sweating and address pain.

The FDA said that the adverse effects were found in approved and non-approved usages and they may be related to overdosing.

“There is no evidence that these reactions are related to any defect in the products’” FDA stated.

The most severe adverse effects were found in children treated for spasticity in their limbs associated with cerebral palsy. Treatment of spasticity is not an FDA-approved use of botulism toxins in children or adults.

The FDA, which is currently reviewing safety data from clinical studies submitted by the manufacturers of Botox, Botox Cosmetic and Myobloc, said that until its investigation will be completed doctors and patients should watch for signs of botulinum effects in the body such as weakness, trouble swallowing or respiratory distress.

Last month, Public Citizen Health Research Group has petitioned the U.S. Food and Drug Administration to require the strongest possible warning, highlighted in a “black box,” on Allergan Inc’s Botox and Solstice Neurosciences Inc’s Myobloc. The request followed reports of 16 deaths after the botulinum toxin spread inside the body.