Douglas Maher - All Headline News Staff Reporter

The FDA is investigsting whether the deaths are related to inappropriate use of the painkiller, or factors related to the product's quality.

At least some may have been accidental overdoses, and some reports suggest that patients or those prescribing the medication were not aware of crucial safety information on the drug's label, said the FDA's Robert Meyer, according to the Washington Post.

The Washington Post reports the warnings in patient information sheets, issued by the FDA: