Iranian officials are investigating the suspected poisoning of hundreds of schoolgirls across the country.

Since November 2022, nearly 700 girls across 30 schools in three cities have allegedly been poisoned by toxic gas in their classrooms, with many reporting symptoms of nausea, fatigue, dizziness and respiratory problems, BBC News reported.

No one has died from the poisonings but over a hundred students have been hospitalized after reportedly smelling gas in their schools, per NBC News.

Where have the suspected poisonings taken place?

The first suspected poisoning occurred in November 2022 in Qom, Iran, where many students at the Noor Yazdanshahr Conservatory became sick, then became sick again the next month.

Since then, around 30 schools in Qom, Tehran and Boroujerd have been attacked.

Who is behind the suspected poisonings?

No one has been arrested and no suspects have been named. However, officials believe the attacks are intentional and could be a deliberate attempt to shut down schools and prevent girls from receiving an education.

Younes Panahi, a deputy health minister, stated, “After several poisonings of students in Qom schools, it was found that some people wanted all schools, especially girls’ schools, to be closed,” per The Associated Press.

He later clarified that he meant that the information indicates “the possibility of criminal and premeditated acts,” according to BBC.

Some, including journalist Jamileh Kadivar, suspect “subversive opposition” groups or “domestic extremists” are behind the attacks, The Associated Press reported.