The Qualifications Authority is investigating whether some students' online exam answers have been lost.
It said about 8000 students at 52 schools sat some of their NCEA exams online this year and it was looking into fewer than 10 reports of lost work.
There was one notable problem, when more than 800 students sitting level 1 English lost their connection to the exam server for a short period.
The authority said it would not provide any more information until it had finished processing students' results.
It is planning a major expansion of online exams next year when it expects to offer about a third of all text-based exams in a digital format.