The U.S. Food and Drug Administration (FDA) is investigating reports of the deaths of patients who were using pain patches that contain the narcotic fentanyl.
The fentanyl patches made by Johnson & Johnson are sold under the brand name Duragesic.
Mylan Laboratories also markets a generic version.
Last month Johnson & Johnson told doctors that it was adding warnings to the Duragesic label about the potential for abuse and misuse of the product.
The FDA says it is presently conducting an investigation into the deaths associated with these patches.
They are apparently examining the circumstances in which the product was used to established if the reported adverse events may be related to inappropriate use of the patch, or factors related to the quality of the product.
The FDA advises that patients follow directions on how to use the patch properly in order to avoid an overdose.
Officials at Johnson & Johnson and Mylan are yet to comment.