"If there are any people involved in the matter, and there certainly are... the perpetrators must be given the most severe of punishments," he warned.
More than 1,000 girls at dozens of schools have been affected by unexplained illnesses since November.
Incidents were reported in at least 15 cities and towns on Sunday alone. มวยพักยก458
Authorities have released very little information about their investigations and announced no arrests, but they have accused Iran's "enemies" of using the suspected poisonings to undermine the clerical establishment.
Some Iranians believe the girls' schools are being targeted by hard-line elements to stop them receiving an education.