ATLANTA (AP) — A U.S. Food and Drug Administration official is warning of the dangers of powdered pure caffeine after the deaths of a Georgia man and an Ohio teenager.

Michael Landa, director of the FDA's Center for Food Safety and Applied Nutrition, wrote about the two men on the FDA's website this week.

Landa said 18-year-old Logan James Stiner died May 27 in Ohio after taking powdered pure caffeine. His parents traveled to Washington from LaGrange, Ohio, this month to urge regulators to ban sales of the substance.

James Wade Sweatt of Alpharetta, Georgia, a 24-year-old recent University of Alabama-Birmingham graduate, died June 24. Landa wrote that his death came after a coma caused by using powdered pure caffeine.

Landa wrote that the substance can be purchased online, and stressed that people should avoid using it.