TOKYO (Kyodo) -- Multiple examinees who took a Japanese language test for non-native speakers in December submitted papers deemed ungradable, a source at the Foreign Ministry said Friday, amid a discovery of an answer leak online.

The Japan Foundation, which administers the Japanese Language Proficiency Test abroad, reported to the ministry that there was an "extremely unnatural" concentration of identical responses. But it did not recognize it as a case of cheating or reveal the number of examinees whose tests were left ungraded.

The five-level test, held up to twice a year in Japan and overseas, was taken by a record 1.26 million people in 2023. Certification in the multiple-choice test's upper levels is commonly sought by employers and academic institutions in Japan as a condition for accepting foreign candidates.

The latest case, involving test takers in Japan and several other countries, could bring under scrutiny the administration of the exams, which are of increasing importance as Japan seeks to accept more foreign labor to support its graying society.

The ministry instructed the foundation in late January to prevent a recurrence, the source said.

It appears the same responses could be due to a leak on social media after the tests were held earlier in China than in other countries, including Japan. The foundation learned of the answers being leaked online and reported it to the ministry.

While acknowledging activity on social media may have influenced the answers, the foundation said in a statement that a "direct causal relationship is unknown." Citing operational reasons, it said it will not offer retakes of the December test.

The issue in question affected the test's second-highest N2 level, taken by more than 230,000 people in Japan and overseas on Dec. 1, 2024. The N2 and higher N1 levels are required for higher education study in Japanese.

Japan Educational Exchanges and Services, the association that runs the test in Japan, sent notices to affected students' language schools, informing them their papers could not be graded and their test fees would be reimbursed.

At one school in western Japan, two of its 140 students who took the test were informed their submissions were ungradable.

"The information leak occurred due to faults in the way the test is managed. Responsibility for it shouldn't be pushed onto examinees, who are in the weakest position in this case," a teacher at the school said, calling for them to be allowed to sit the test again.