The incident allegedly happened at the Nghia Thang Secondary School in Tu Nghia District, Quang Ngai Province, according to Nguyen Dang Vinh, the district's chairman, who was interviewed by Giao Thong newspaper on Wednesday.
The official said that the police investigation into the incident is still underway and that there is still no conclusion.
Police began to look into the case after receiving a report from the school, after the girl's mother filed an accusation.
According to the girl, in mid-November, the three boys had taken turns raping her in a school restroom.
At the time of the alleged incident, no one reported hearing or seeing anything out of the ordinary.
Following the accusation, the three boys continued to attend classes and to take part in other activities as normal.
The mother only learned about the incident later, when her daughter told her what had happened.