By Victoria Bisset and  Babak Dehghanpisheh 

Dozens of students in Iran were hospitalized for suspected poisoning this week, the latest in a series of mysterious cases at girls’ schools across the country.

Emergency services in Pardis, on the outskirts of Tehran, transferred 37 schoolgirls for treatment on Tuesday, a school official told Iran’s semiofficial Tasnim news agency. He said the students were suffering from “mild poisoning” and added that all of the girls are expected to recover.

The same day, the activist-run Human Rights Activists News Agency reported that several other female students fell ill in the city of Qom, to the south of the capital, where many of the suspected poisonings have taken place.

Such incidents have been reported in 10 to 15 cities across Iran in recent months, Abdulali Rahimi Mozafari, a member of Iran’s parliament, said Tuesday, according to the Entekhab news website.

The number of affected students across the country is unclear, but Zahra Sheikhi, a spokeswoman for Iran’s Health Commission, said Wednesday that 800 students had suffered “mild poisoning” in Qom alone in recent months, the reformist newspaper Shargh reported.

While some boys also appear to have fallen ill, the vast majority of cases appear to be at girls’ schools. No deaths have been reported.

Videos posted on social media Wednesday showed furious family members protesting outside some of the affected schools in Tehran; in one video, a member of Iran’s security forces can be seen pulling a woman by the hair. Another video from the capital shows girls chanting “death to the child-killing government.”

“The deliberate poisoning of school girls in Iran is exposing the fanatical, lawless and violent mentality that is resurfacing under this unaccountable government, [which is] trying to force the entire country, especially women, backward,” said Hadi Ghaemi, executive director of the Center for Human Rights in Iran.

In a visit to Qom on Tuesday, Iran’s health minister, Bahram Einollahi, said the poison was “very mild” and that the students’ symptoms included muscle weakness, lethargy and nausea, the Iranian Students’ News Agency reported. According to the Associated Press, some of the children described smelling tangerines, chlorine or cleaning agents. Sheikhi, the Health Commission spokeswoman, said the poison appeared to have been inhaled.

Alireza Monadi, the head of the parliament’s education committee, said Wednesday that Ministry of Health tests had detected nitrogen gas in the poison spread at schools in Qom, according to the Hamshahri newspaper.

The reason for the poisonings remains unknown. Last week, Iranian Attorney General Mohammad Jafar Montazeri ordered an investigation and said the spate of poisonings “indicates the possibility of intentional criminal actions.”

On Sunday, Iranian news outlets quoted Younes Panahi, a deputy health minister, as saying that schools were being deliberately targeted. He told journalists that the culprits “wanted all schools, especially girls’ schools, to be closed,” according to Iran’s Ettelaat newspaper. He later denied making the comments, saying he could not confirm whether the poisonings were intentional or why they had taken place.

While education in Iran is only compulsory for children between 6 and 11, Iran’s government has a strong focus on education, with women accounting for more than 50 percent of Iran’s university students, according to the World Bank. Tehran has repeatedly pressed the Taliban in neighboring Afghanistan to overturn its ban on girls’ education.

Families of the students affected in Qom, an important site of Shiite Muslim shrines and scholarship, held a protest recently to demand that authorities take action, Hamshahri reported.

The country has already been gripped by months of protests sparked by the death of 22-year-old Mahsa Amini while in police custody for allegedly wearing a hijab improperly in public. While the demonstrations started over women’s dress, they morphed into rallies against the country’s theocratic state, crossing age, gender, ethnic and class lines. It’s not clear at this point whether the suspected poisonings are linked to these protests.

Students have played a key role in the protests, and more than 700 of them have been arrested, according to the Volunteer Committee to Follow Up on the Situation of Detainees.

Authorities have launched a brutal response, with HRANA, the activist news agency, reporting that at least 530 demonstrators have been killed since the unrest began in mid-September. At least four protesters have been executed, while others have received death sentences.

By Victoria BissetVictoria Bisset is a breaking-news reporter for The Washington Post's London Hub, covering the most urgent and consequential stories as they unfold on the European day.