Nearly a thousand Iranian schoolgirls have been taken to hospitals in more than 10 cities after falling ill with respiratory, cardiac and neurological symptoms, as the international community called for an urgent investigation. Senior Iranian officials believe that the girls, suffering from nausea, dizziness and fatigue, may have been deliberately poisoned. Many in <a href="https://www.thenationalnews.com/mena/iran/" target="_blank">Iran</a> believe it is an attempt to force girls' schools to close and to deny them an education. The call to action came as authorities arrested four people on Thursday in connection with an assault on a woman outside a girls' school targeted in a wave of poisoning attacks, a news agency said. On Wednesday, the <a href="https://www.thenationalnews.com/world/us-news/" target="_blank">US</a> urged authorities in Iran to investigate the suspected poisoning attacks of recent months. “What we want to see … is these reported poisonings come to an end. We want to see this stop”, said US State Department spokesman Ned Price. “These are very concerning and disturbing reports that we’ve all read in the press. But it is incumbent on Iranian authorities to respond. It is incumbent upon them to put an end to these reported attacks. It is incumbent on them to hold accountable those who may be perpetrating this.” On Wednesday, Iran's President stepped in after more than 100 pupils were admitted to hospital. The President's website said Ebrahim Raisi had assigned Interior Minister Ahmad Vahidi to provide “continuous information on the results of the investigation” into the attacks. At least 10 girls' schools were targeted in the latest suspected attacks on Wednesday, seven in the north-western city of Ardabil and three in the capital, media reports said. The incidents in Ardabil left 108 pupils in hospital, all in a stable condition, said state-linked news agency Tasnim, which also reported poisonings at three schools in Tehran. Mr Vahidi held a press conference on Wednesday, at which he debunked earlier reports from Fars news agency that security forces had detained three people over the wave of suspected poisonings. “There are various reports that are completely false," he told journalists, adding that reports of the detection of a specific chemical substance being used in attacks were incorrect. Parliament's website had said health ministry tests on a substance found at the schools in the holy city of Qom — where 800 pupils were affected — had detected traces of nitrogen, which is mainly used in fertilisers. The poisonings first started in the city of Qom, where 18 girls were taken to hospital on November 30, according to Iranian state media. Another incident was reported in Qom on February 14, when more than 100 pupils from 13 schools were taken to hospital after what Tasmin described as “serial poisonings”. In Tehran, 35 schoolgirls were admitted to hospital on Tuesday, according to Fars News. They were reported to be in a “good” condition, and many of them were discharged, it said. Pupil poisonings have also been recorded in recent months in the city of Borujerd in Lorestan province and in Chaharmahal and Bakhtiari province. Most of the incidents have taken place at girls’ schools, but state media have also reported at least one incident of suspected poisoning at a boys’ school in Qom, on February 4. <i>With reporting from agencies</i>