The study volunteer who died during research at the Johns Hopkins Asthma and Allergy Center was an otherwise healthy woman. Ellen Roche was employed at the Center and volunteered to participate in a study in which she was required to inhale a blood pressure medication known as hexamethonium. Roche died one month after inhaling the drug.

Researchers are baffled as to why the woman died. The investigation centers on hexamethonium's tendency to constrict the airways in the human body. Johns Hopkins and the National Institutes of Health have warned other research facilities throughout the United States to pay close attention to study participants who inhale hexamethonium.

On Thursday, the U.S. Department of Health and Human Services announced that it was launching an investigation into the incident. According to the Department, research programs "should reassess protocols involving inhalation of hexamethonium and, if necessary, consider temporarily suspending the research in light of this event."

While study volunteers were warned that hexamethonium could lower blood pressure and cause dizziness, they likely were not told that inhalation of the drug could cause death.