Up to 74 schoolgirls in Afghanistan's far north fell sick after smelling gas and were being examined for possible poisoning.
There have been numerous cases of mass poisonings of schoolgirls by elements of Afghanistan's ultra-conservative society that are opposed to women's education.
Local officials said the girls became ill after smelling gas at their school, Bibi Maryam, in Takhar province's capital, Taluqan.
The city is about 250km north of the country's capital, Kabul.
The Takhar governor's spokesman, Sulaiman Moradi, blamed "enemies of the government and the country" for the mass illness and said the aim was to stop girls from going to school.
The girls were taken to the provincial hospital and most were released after being treated.
Several remained in a critical condition.
Blood samples have been sent to the Ministry of Public Health to ascertain the cause of illness.
The apparent poisoning came three days after more than a dozen students fell ill in another girls' high school in Taluqan.
No-one has claimed responsibility for either incident.
Between May and June last year there were four poisoning attacks on a girls' school in Takhar.
Takhar has been a hotbed of militancy and criminal activity since 2009, with groups such as the Taliban and the Islamic Movement of Uzbekistan active.
Since the 2001 ousting of the Taliban, which banned education for women and girls, girls have returned to schools, especially in Kabul.
But periodic attacks against school girls, their teachers and their school buildings, continue.
Afghan women have won back basic rights in education, voting and employment since 2001.
Fears are growing that such gains could be traded away as Western forces prepare to leave and the Afghan government seeks peace talks with the Taliban.