Exam officials have apologised for a glitch on Thursday morning with an app for the DSE public exams.

The Examinations and Assessment Authority said those who sat the Chinese language exam were able to use the app to mark their attendance, but invigilators had problems checking such records and counting answer sheets.

In a statement, it stressed all exams started on time as invigilators switched to manual checks as part of their contingency plans.

"We have reviewed why [the app] was unable to run smoothly, and discovered that when it was in full operation, the app didn't function well when the system had to handle a large amount of data," the exams body said.

It said it will continue to use the app for the English language exam on Friday morning.