In the meantime, an office assistant named Shahanara Begum Shanu locked the door of the washroom from outside without checking if anyone was inside.
As the girl was speech-impaired, she failed to raise an alarm, police said.
Later around 10.00pm that day, Al Amin, a resident of the area, heard the groaning sound of the girl from inside the washroom. He immediately broke open the door of the washroom with the help of local people and rescued the girl.
Amir Hossain, headmaster of the school, said, “I left the school around 4.30 pm but had not spotted anyone on the premises then.”
Shahrasti upazila nirbahi officer (UNO), Shirin Akter, said, “A probe has been ordered to find out if there was any negligence on the part of the school authorities. Action will follow, after the probe report."
The headmaster and the president of the school managing committee met the girl's family on Friday and offered their apologies