Almost 29,000 pupils in Scotland have received their exam results a day early by mistake, the Scottish Qualifications Authority said.
All 29,863 pupils who selected to receive their results via text message were sent them, ahead of the official delivery day on Thursday.
The SQA said it is making inquiries with the external contractor which sends out the texts on its behalf.
Almost 160,000 pupils are due receive their results in the post, and 36,000 signed up to get theirs electronically via text message or e-mail as well.
Those opting for a text message alert received them at around lunchtime on Wednesday.
Scottish Labour's education spokesman Ken Macintosh said: "This is a serious mistake and will cause concern for the tens of thousands of people who have not had a headstart in their results. There should be a level playing field, especially because the clearing system is live and searchable from midnight."
Mr Macintosh said the SQA had made "serious mistakes" with results in the past. The SQA was investigated in 2000 when thousands of certificates went missing and thousands more results were incorrect.
Scottish Liberal Democrat leader Willie Rennie MSP said: "This is extremely unprofessional and will create a great deal of anxiety and stress for pupils already anxious and stressed."
Scottish Government Education Secretary Michael Russell said: "We have acted swiftly to ensure that the pupils who have received a text message earlier than expected are receiving the exact same level of support as all pupils will receive tomorrow.
"We have opened the exam results helpline today, and pupils can call and get a range of advice, support and help from expert advisers. I have also asked SQA for an urgent explanation of how the error occurred."
