The results online website has been out of action since Tuesday

The Scottish Qualifications Authority said it had disclosed information which could have compromised the names and login details of up to 30 candidates.

The error occurred when the SQA reissued more than 3,300 password and login details to people having trouble accessing the online results service.

Login details for other users were added by error to some e-mails.

More than 155,000 people received their exam results by post on Tuesday.

Login details

About 35,000 had opted to access their results online a day early but many experienced problems with the new service.

A missing 's' in the web address provided in letters to candidates meant that many spent hours unsuccessfully attempting to access the results site.

Thousands of people also contacted the SQA on Monday and Tuesday to say that they needed to be reminded of their login details.

On Tuesday morning, the SQA discovered that it had made an error which could possibly have meant someone else viewing the results of another candidate.

SQA spokesperson Mike Haggerty said the results online service had been "locked down" on Tuesday, as soon as they were notified of the mistake by a candidate.

Computer experts checked the records and isolated 30 potential cases where the security could not yet be guaranteed.

Mr Haggerty said all those potentially affected had been informed.

He said: "We are really sorry to have put these candidates into this unsatisfactory position and are working hard to resolve these issues.