An Iranian deputy minister said "some people" were poisoning schoolgirls in the holy city of Qom with the aim of shutting down education for girls, state media reported.
Since late November, hundreds of cases of respiratory poisoning have been reported among schoolgirls mainly in Qom, south of Tehran, with some needing hospital treatment.
Deputy health minister Younes Panahi, implicitly confirmed the poisonings had been deliberate.
"After the poisoning of several students in Qom schools, it was found that some people wanted all schools, especially girls' schools, to be closed," the IRNA state news agency quoted Panahi as saying.
He did not elaborate. So far, there have been no arrests linked to the poisonings.
On February 14, parents of students who had been ill had gathered outside the city's governorate to "demand an explanation" from the authorities, IRNA reported.
The next day government spokesman Ali Bahadori Jahromi said the intelligence and education ministries were trying to find the cause of the poisonings.
Last week, Prosecutor General Mohammad Jafar Montazeri ordered a judicial probe into the incidents.
The poisonings come as Iran has been rocked by protests since the December 16 death in custody of 22-year-old Iranian Kurd Mahsa Amini for an alleged violation of country's strict dress code for women.