The stricken girls suffered from headache, fever and nausea, Khaama Press reported. They were hospitalized.
Tests at Hazrat Imam Zada Yahya high school in Sar-e-Pul province failed to determine what caused the girls' illness. Officials also said they had no motive for the attack, if that was what it was.
Incidents of female students being poisoned have been reported elsewhere in Afghanistan, including the Kabul region. The motive appears to be a religious conviction that women should not be educated.
Notable deaths of 2014 [PHOTOS]