Members of the northern province's national high school examination board that are suspected of involvement will also be investigated for "abuse of power or position in performance of official duties."
The criminal investigation was launched after inspectors from the education ministry concluded on Monday that the province's examination board had committed multiple violations.
Upon re-grading 110 Literature test sheets that had unusually good results, inspectors found that the original scores for 42 sheets were higher than what they should've been, 12 of them by as much as 4.5 points.
Inspectors also found that a number of multiple-choice answer sheets were altered prior to being submitted to the ministry for grading.
They concluded that Son La's national high school examination board had violated regulations in grading, storing and transferring the candidates' test sheets.
Specifically, the board had copied scans of the candidates' answer sheets on to a CD disc without authorization and taken it out of the designated secured area.
They also failed to properly secure the grading area and did not seal the room and boxes used for storing the candidates' physical test sheets, as well as the computer used for grading, as required.
Inspectors said five members of the board were involved in the violations, including Tran Xuan Yen, deputy director of Son La's Education Department.
This criminal investigation follows just a week after the first one was launched in Ha Giang Province, also in the northern highlands.
The investigation in Ha Giang has resulted in the arrests of two senior education officials.
Vu Trong Luong, deputy head of the Testing and Quality Assurance unit in Ha Giang's Education Department was found to have heavily altered the results of over 330 test sheets belonging to 114 candidates to increase their scores.
Luong's direct superior Nguyen Thanh Hoai was arrested for enabling Luong to commit his crime by giving him the key to the room where candidates' test sheets were stored.