With R for Results Day three weeks away, the authority has taken the unusual step of publicising the discovery of a marker who has failed to meet the normal criterion of at least three years relevant teaching experience. Fewer than 200 scripts are involved.
A special inquiry is already under way amid the more wide-ranging inquiry into marker recruitment and appointments.
An SQA spokesman said: "Through our quality assurance procedures, we have uncovered an issue regarding the marking of an allocation of examination scripts. It appears that these scripts were marked by an individual who does not meet SQA's criteria for appointment."
He added: "The papers in question have now been fully checked individually and no marks have required to be changed. Therefore the candidates involved are in no way disadvantaged."