LONDON (Reuters) - Students in Asia have been notified that their scores on the writing section of last month’s ACT college-entrance exam are being canceled, in the latest example of how standardized test makers are struggling to contain an international epidemic of cheating.

Students attend a lecture for the entrance exam for postgraduate studies at a hall in Jinan, Shandong Province, China, July 18, 2016. Picture taken July 18, 2016. China Daily/via REUTERS

The incident comes just months after ACT Inc, the Iowa-based nonprofit that operates the test, was forced to cancel its exam for all takers in South Korea and Hong Kong. That incident, in June, marked the first time the high-stakes exam was canceled for an entire country.

ACT spokesman Ed Colby declined to say how many students were affected by the October score cancellations, which he said involved test centers in Asia and Oceania. He described the incident as the result of “a compromise in the testing process” and said the affected students “amounted to only a small portion of examinees in the region.”

Affected students for the October score cancellation received a message from ACT that stated: “Unfortunately, events occurred which compromised the testing process for the writing portion of your test event. As a result, you will not receive a score for your writing test response/essay. Your multiple choice ACT tests—English, mathematics, reading, and science tests—WILL be scored.”

The message added that ACT will issue each student a $16 refund.

The ACT writing section is nominally voluntary, but many colleges require students to take it to gauge an applicant’s writing and reasoning abilities.

The latest security incident is “a frustrating and complicated situation for our students,” said Kristin J. Dreazen, president of the international affiliate of the National Association for College Admission Counseling.

The day before the ACT was administered on Oct. 22, Reuters obtained a copy of an ACT writing test on the subject “Fame” that an Asian source said had leaked and was to be given the next day. Test administrators in Asia were instructed shortly before the test to substitute a different essay topic than the one that originally had shipped. Colby declined to comment on the test Reuters obtained.

Reuters reported in July that ACT’s test security unit repeatedly had recommended tightening security overseas before the June breach, but that ACT executives had rejected the recommendations. The organization later laid off the head of the unit. ACT’s chief executive, Marten Roorda, has declined to be interviewed.

ACT recently began shipping some of its test booklets and answer sheets in lock boxes to guard against leaks. But the use of lock boxes still is not universal, according to test administrators.

In July, Reuters also detailed widespread cheating in the ACT-owned Global Assessment Certificate program. The program, which offers college preparatory courses, has about 5,000 students and operates in about 200 centers, mostly in Asia. reut.rs/2akY3uf

Seven students who attended three different GAC centers in China described how school officials and proctors ignored and were sometimes complicit in cheating on the ACT. Eight teachers or administrators who have worked at seven different Chinese GAC centers also described cheating in program courses.

ACT’s chief rival, the New York-based College Board, which administers the SAT, has been struggling with its own security problems. The College Board recently notified an undisclosed number of test-takers in Egypt that their scores were being canceled for the October test.

College Board spokesman Zach Goldberg said the cancellations were “based on evidence that a test preparation organization illegally obtained and shared the test content before the administration.” He declined to elaborate.

Reuters also reported in August that a major breach exposed hundreds of unpublished questions for upcoming SAT exams. A College Board spokeswoman said the organization was investigating what she termed “a serious criminal matter.”

The SAT and ACT are used by thousands of U.S. colleges to help choose from among millions of student applicants.

Read the entire Reuters Cheat Sheet series here