Police on Saturday said they've arrested a local secondary school teacher for allegedly posting online a confidential marking scheme of this year's university entrance exams.

Officers said the 38-year-old man, surnamed Wong, was taken away on Friday on suspicion of violating the Examinations and Assessment Authority Ordinance.

Exams authorities earlier reported the case to the police after the document's cover was posted on social media platform Xiaohongshu.

Officers said the suspect claimed to be a marker for the Diploma of Secondary Education exams and posted the marking scheme of the Chinese-language paper twice in May and July this year.

"Although he had claimed to be an exam marker online, he was never a staff member of the Examinations and Assessment Authority, nor an exam marker," said senior inspector Chan King-lok.

"We do not rule out that he was hoping to use the authority's confidential document as a selling point, to attract students to enrol in some private tutoring classes and earn money from that."

Chan said officers would continue to look into where the suspect obtained the confidential document from.

Police did not ruling out making further arrests.

The Examinations and Assessment Authority said it will not comment on the case, which is now under police investigation. The authority stressed that it has all along attached great importance to the confidentiality and fairness of public examinations, and that anyone appointed or employed must keep all matters in secrecy, including their identity as exam personnel.