At least 84 Afghan schoolgirls were admitted to a hospital Tuesday for headaches and vomiting in the third apparent poison attack on a girls school in as many weeks, officials and doctors said.

The students were lining up outside their school in northeastern Afghanistan on Tuesday morning when a strange odor filled the school yard, and one girl collapsed, said the school's principal, who was herself in a hospital bed gasping for breath as she described the event.

"We took her inside and splashed water on her face," said Mossena, who like many Afghans goes by one name. Then other girls started passing out in the yard and they sent all the students home.

It was unclear if the incident was a deliberate attack on the school, though the Taliban and other conservative extremist groups in Afghanistan, who oppose girls education, have been known to target schoolgirls.

Mossena said she did not know what happened next because she collapsed and woke up in the main hospital in Muhmud Raqi, the capital of Kapisa province, which lies just northeast of Kabul.

At least 98 patients were admitted from Aftab Bachi school, including the principal, 11 teachers and two cleaners, said Khalid Enayat, the hospital's deputy director. He said about another 30 students were being monitored to see if they developed symptoms, although they were not admitted to the hospital. An official earlier said 89 schoolgirls had been hospitalized.

Click here for photos.

Tuesday's apparent attack is the third alleged poisoning at a girls' school in less than three weeks. It comes one day after 61 schoolgirls and one teacher from a school in neighboring Parwan province were admitted to a hospital after complaining of sudden illness. They were irritable, confused and weeping, and several of the girls passed out.

The patients in Kapisa complained of similar symptoms to those in the Parwan incidents -- headaches, vomiting and shivering, said Aziz Agha, a doctor treating the girls.

"I got dizzy and my head hurt. Some other students took me home, then I passed out and they brought me to the hospital," said a startled looking 11-year-old, Tahira, from her hospital bed.

The fifth grader said she planned to go back to school when she felt better, but that now it would fill her with fear.

"I'm going to be scared when I go back to school. What if we die?" she said.

Interior Ministry Spokesman Zemeri Bashary said officials suspect some sort of gas poisoning, and that police were still investigating.

Under the Taliban's 1996-2001 regime, girls were not allowed to attend school. Though it was unclear if the recent incidents were the result of attacks, militants in the south have previously assaulted schoolgirls by spraying acid in their faces and burning down schools to protest the government.

Scores of Afghan schools have been forced to close because of violence. Still, the three recent apparent poisonings have taken place in northeast Afghanistan, which is not as opposed to education for girls as Afghanistan's conservative southern regions.

The first apparent poison attack took place late last month in Parwan, when dozens of girls were hospitalized after being sickened by what Afghan officials said were strong fumes or a possible poison gas cloud.