The incident occurred yesterday in Rahim Yar Khan district, 400 kms from here.
Officials of a state-run rescue service said that students started fainting shortly after classes began at the Government Girls Higher Secondary School in Kot Samaba.
The school's administration called the rescue service, whose personnel shifted over 60 students and two female teachers to Sheikh Zayed Medical College Hospital.
Doctors said they were out of danger.
"Owing to the timely response, lives of over three dozen schoolgirls and the teachers were saved," a rescue service spokesman said.
The school's administration believes the incident occurred due to a leak of gas from a pipeline adjacent to the building.
An official of the gas utility, however, said gas was not passing through pipelines that were recently installed near the school and that the incident may have occurred due to a leak of gases in the school's science laboratory.
Punjab Governor Makhdoom Ahmed Maehmood directed the managing director of Sui Gas Company to take action against those responsible for the incident.
