Five Afghan teachers and 40 of their pupils, most of them girls, have been admitted to hospital with severe headaches after a suspected airborne poison attack, the Public Health Ministry said on Monday.
They fell ill on Sunday afternoon during a ceremony at a school in the Sadiqi district of Parwan province, some 70 km (40 miles) north of the Afghan capital, Kabul.
"Among them there are 5 adults and 40 children, most of them girls, who have been affected," Dr Abdullah Fahim, spokesman for the Public Health Ministry said. "For the time being, it seems to be airborne poisoning. But it's not confirmed yet what the actual reason is," Fahim said.
Attacks on girls schools have increased in the past year, particularly in east and south Afghanistan. Last year a group of schoolgirls in Kandahar had acid thrown in their faces by men who objected to them attending school.
Until 2001, when the Taliban were overthrown by US- and Afghan-led forces, women were prohibited from going to school or work, but Parwan is a relatively safe area of Afghanistan, not known for Taliban activity.
Fahim said he could not rule out terrorist involvement in the incident, and that he expected blood test results to provide more information on what had affected the 45 victims.
"At this stage we cannot deny any suspected terrorist activity. I hope maybe this evening or tomorrow we will have some more information from the blood tests," Fahim said.
The governor of Parwan, Abdul Jabar Taqwa, told Reuters he had visited the hospital and most of the patients had recovered and appeared to be in good health.
"The Ministry of Public Health, the toxicology department and police are involved in the investigation. As with most casualties we are full of concern especially as it's airborne," Fahim said.