At least 60 girls at a school in the eastern Afghan province of Paktika fainted on Wednesday after possibly being poisoned, an official told Efe.
The incident occurred at the Samin Akbari girls' school, said Rula Samun, a spokesperson for the provincial government.
"There were 60 girls with discomfort ... but 20 of them improved after receiving first aid at the hospital," he said.
The girls are said to be out of danger.
Samun told the AIP news agency that the students began feeling badly after drinking water from a nearby well and that the odor of a strange gas was detected in the area.
However, Paktika's police chief, Zalmai Oriyakhel, ruled out contamination of the water and said that the cause of the problem was that a student sprayed something from an aerosol can into a classroom.
"I can confirm that the water was not contaminated. I myself drank that water. We're investigating the incident," he said in remarks to Efe.
Poisoning cases at girls' schools are rather frequent occurrences in Afghanistan and generally they take place amid rather mysterious circumstances.
The most recent case was registered on June 2, when 20 students were apparently poisoned.
In addition, in May 80 girls fainted in another similar incident in Faryab province.
Many analysts blame the poisonings on the Taliban, but spokesmen for the rebels have denied any involvement in the incidents.
The insurgents, however, oppose educating young girls and female teenagers and - in fact - prohibited it during their 1996-2001 rule. EFE