The fresh body has been formed as questions were raised against the investigation conducted by the previous investigation committee, said Deputy Commissioner Mohammad Shahriaz.
The newly formed probe committee will submit their report within seven working days, DC said.
On December 28, last year the victim was alleged to have been sexually assaulted by Rezaul Karim, Office Assistant of Hatiandaha Girls School and College.
The students of the institution also staged demonstration protesting the molestation of their fellow student at the college premises on Wednesday.
Superintendent of Magura Police (SP) Liton Kumar Saha said the victim along with her younger sister went to the school on December 28 for admission process while Rezaul Karim was working alone at the office.
Karim took the girl to an empty room beside the officer and molested her, according to the complaint.
Later, people rushed to the spot after hearing the scream of the victim and rescued her.