The results were sent to 2075 students on Wednesday night.

When some students registered to receive their Australian Tertiary Admission Ranks, they were immediately sent results in a text message, five days ahead of the official release.

It's understood this happened in a window of less than an hour from about 7pm.

VCE Facebook sites were filled with reports from students wondering if they have received their real results or if they had been victims of a hoax. Fairfax Media has also been contacted by scores of concerned parents.

The SMS service used by the Victorian Tertiary Admissions Centre (VCAT) and the Victorian Curriculum and Assessment Authority (VCAA) is handled by external provider Salmat Digital.

Salmat has provided SMS services for VCE results for several years. It also provides marketing and other services for the Commonwealth Government, Telstra, Coles, Big W, Target and others.

Suzanne Connelly, a spokeswoman for VCAT and VCAA said the SMS service had been tested extensively in the past few weeks, and none of the problems reported by more than 2000 students had been replicated.

"They [Salmat] shut it down as quickly as they could on Wednesday night," Ms Connelly said.

She apologised on behalf of the agencies involved, and said: "at the moment our emphasis is on the students who have received their results and their ATAR, if they were eligible for one."

She said all schools had been contacted to inform them of the error, and VCAT and the VCAA had been in contact with all students who had received their results and/or their ATAR early, to offer them support.

Ms Connelly said it was too early to discuss whether VCAT and the VCAA would pursue penalties against Salmat.

Education Minister James Merlino has ordered an urgent investigation into the blunder, which has compromised sensitive results that are normally closely guarded until the official release.

He said on Thursday morning that he wanted the investigation completed as quickly as possible.

"This is obviously a serious error that has been made and I can understand that students would be confused and angry and disappointed with what has occurred.

"I can assure parents, the students and their schools that there'll be a thorough independent investigation to find out what went wrong, how it happened, and to ensure it doesn't happen again."

The saga is a major embarrassment for VTAC, who vowed just weeks ago to crack down on schools that leaked ATARs.

It imposed a range of new penalties for schools that broke the rules, including being barred from accessing early results for up to five years.

The principals of some students who got early results said the study scores were close to what they would have expected the students to get. Some also pointed out the hypocrisy of VTAC's threats to punish schools for releasing the data early.

While the VCAA calculates study scores for individual subjects based on school assessments and exams, VTAC calculates the ATAR which is used by universities.

Disbelief, elation, shock and anger spread through students'  online forums as some students expressed devastation at receiving their results early, while others were furious they couldn't access theirs.

"ATAR is done and dusted, relieved," one student posted.

"I'm actually more nervous about my ATAR now that some people have gotten theirs like, All Hope Is Dead," another wrote.

Screen grab of a reported VCAA text received by a year 12 student Photo: Supplied

Lynda Manley, mother of Princes Hill Secondary College student Ruby, said on Wednesday night she was angry that her daughter received a text at a time when there were no support systems available to help students process the news.

"It's 8 o'clock on a Wednesday night and the school support systems are ready to kick in on a Monday morning. I can't raise teachers on a Wednesday night.

"We've got no way of confirming whether this is a hack or legitimate."

Ruby tried to get her ATAR after reading on the VCE DiscussionSpace Facebook page that others were getting their results. The text she received back "was not the score she was hoping for," said Ms Manley.

"Now I've got this upset 18-year-old. I'm thinking this has got to be a prank or a hack."

Toni Buttigieg, who came home from work to find her daughter in tears, said the early unexpected release had caused already-anxious students an enormous amount of stress.

"There is enough pressure on VCE students and to have results come early without knowing whether they are real or not has just exacerbated the anxiety.

"We've been working towards Monday morning, we've put strategies in place but tonight because of the unexpected, it's just blown up. We have vulnerable young people and they just don't know, they don't know if it's real."

However, not everyone was disappointed.

Isaac Black, 18, was with a group of friends when they saw a post on a VCE Facebook group by a girl who'd discovered the error.

Soon, all of his friends had their results too, and all were happy with their results.

"We all got the scores that we needed to get in to our courses," he said.

Keira Schaefer, Isaac Black, and Grace Pear were happy with their VCE results. Photo: Isaac Black

The text message sent to Isaac apologising for his results being sent early. Photo: Isaac Black

VCE student Paddy received a nice surprise when he registered at 7.45pm - a text message that said he had achieved an impressive ATAR of 99.75. It also included all his study scores for individual subjects.

But he was unsure whether to believe the good news.

"No one is sure what is going on," he said on Wednesday. "It's good news, but I don't know if it is real. I don't know whether to celebrate or not."

He was considering studying a science degree at university next year, but said if the results were correct he would reconsider his options.

"I might take a gap year and have a proper think. It is a lot higher than I thought I would get."

A contribution to the VCE DiscussionSpace Facebook group about the leak.