Wilkinsburg School Superintendent Archie Perrin says the packets were found Tuesday when fourth-graders were cleaning out a desk used by a student at Turner Elementary School who moved out of the district weeks ago.
The school's principal sent parents a letter to let them know what's going on. The letter doesn't identify the substance, but urges parents to speak with their children about the dangers of drugs.
Perrin says school officials won't be contacting the former student's parents because former students aren't in their jurisdiction.
Wilkinsburg police aren't saying whether anyone will face charges if the powder proves to be drugs.