"I have applied for a big university which admits a few students. If many examinees gain high marks due to cheating, I may lose chances to be admitted," Pham Trang, who has just graduated from Thai Ninh High School in Vietnam's northern Thai Binh province, expressed her nervousness.

Her nervousness is hardly groundless because many students in several provinces, who attended the national high school graduation exam in June, have received high marks not thanks to their good academic performances, but because of cheating committed by education officers.

"According to announcements of the Ministry of Education and Training, among 11 students with the highest marks nationwide, three come from Ha Giang, a poor mountainous province with poor education achievements in recent years, not from Hanoi capital or provinces with tradition of good studies like Thai Binh, our province," Pham Trang told Xinhua on Monday, adding that 65 other students got the mark of nine or higher (10 is the highest) for their physics test.

Some 5,400 students from the mountainous northern province of Ha Giang sat for the exam which was taken by over 900,000 students nationwide.

Examinees took part in four tests with a total of six subjects, including literature, maths and foreign language, and either a group of three natural science subjects or a group of three social science subjects.

The exam is of significance because its results are used for both high school graduation and university entrance consideration.

After realizing the existence of too many abnormally high marks gained by students from Ha Giang and the spread of rumors about exam cheating, Vietnamese Prime Minister Nguyen Xuan Phuc instructed the Ministry of Public Security to probe the incident, Vietnam News Agency reported.

On July 20, Ha Giang police detained Vu Trong Luong, 40, deputy director of the Examination and Quality Management Division under the provincial Department of Education and Training on the charge of "abusing position and power while on duty."

According to investigators, Luong raised marks in 330 multiple-choice test sheets of 114 students from Ha Giang by at least over 1 point each. Marks of some students were lifted by more than 20 points, even those of few students were adjusted up by 29.95 points, or to nearly the absolute marks of 30, Vietnam News Agency reported.

On July 23, the provincial police detained Nguyen Thanh Hoai, 49, director of the division, on the same charge of "abusing position and power while on duty."

He was found to have given the key of the room where the test sheets were kept to Luong, Vietnam News Agency reported. His act violated the exam's regulations.

Local media reported that people used mobile phones to sent text messages which contained the exam codes of the students to Luong so that he could know who was who to adjust up their marks.

Among the students who benefited from the cheating are two nieces and one daughter of Trieu Tai Vinh, Secretary of the Ha Giang Party Committee. According to investigation, the total exam marks of Vinh's daughter were lifted by 5.4 points.

Vinh told local media that he did not ask anybody to raise exam marks for his daughter and nieces, and he did not know that their marks had been lifted.

"It is hard to know why exam marks of 114 students from Ha Giang were adjusted. Some believed that Luong had received a lot of money from the students' parents to raise their marks," Bui Ngoc Quang, a quality assurance officer at the University of Social Sciences and Humanities under the Vietnam National University in Ho Chi Minh City, told Xinhua.

Other people thought Luong raised the marks free of charge, Quang said, explaining that education officials in Ha Giang might have simply wanted to impress their superiors and other localities that Ha Giang's education quality is much better now.

While Vietnamese police were probing the exam cheating scandal in Ha Giang, many people proposed the Ministry of Education and Training and the Ministry of Public Security investigated exam results in other provinces, including the two northern provinces of Lang Son and Son La.

In late July, Sai Cong Hong, vice director of the Quality Management Department under the Ministry of Education and Training, head of the ministry's working team in Lang Son, told reporters that the team had found no abnormalities in the exam in the province, Vietnam Central Television (VTV) reported.

However, the ministry's working team detected wrongdoings in the exam in Son La -- the average mark for the maths test was 3.43, compared with the national average of 4.88. However, 30 students from Son La got marks of nine or higher for their maths test.

On July 23 in Son La, Mai Van Trinh, director of the ministry's Department of Educational Testing and Quality Assurance, told reporters that five local people, mostly local education officials, involved in the exam fraud in the province.

One of the five is Tran Xuan Yen, vice director of the Son La Department of Education and Training, member of the exam steering board, and head of the multiple-choice test marking group.

On July 26, local police started criminal proceedings against the exam cheating scandal in Son La.

"Since 2015, the education ministry has merged the high school graduation exam and university entrance exam into one national exam. Students like us as well as our parents highly appreciate that move because it has saved us a lot of time and cost. But cheating scandals this year have worried us a lot. Next month, whether or not will I be admitted to the university I applied?" Trang asked.

On July 24, following the mark manipulation scandals in Ha Giang and Son La, Minister of Education and Training Phung Xuan Nha announced the ministry would review the organization of the previous national high school exams, especially the process of giving marks to tests, to minimize cheating in future exams.