The poisonings, targeting girls' schools since November, have been ramped up this week with hundreds more girls falling sick across Iran.
Social media videos surfaced on Sunday show that students were poisoned in many cities, including Fouladshahr and some other cities in Esfahan (Isfahan) province, Karaj and Fardis in Alborz province, Tabriz, Yazd, Hamedan, Shiraz, Ramhormoz and Mahshahr in Khuzestan province, Qazvin, Gonbad-e Kavus in Golestan, and the capital Tehran. Only In the city of Yazd, at least eight schools were attacked on Sunday.
On Saturday alone, schools in 33 cities were targeted by the same gas that has already affected around 1,500 students in recent weeks.
The scale of the intentional poisoning of female students -- which started in the religious city of Qom and spread further throughout the country and reached schools in small towns and villages -- has stepped up in recent weeks, becoming a daily occurrence.