The theft, at the university's main campus in Pretoria, was discovered while exams at the country's biggest university were under way. According to the police, copies of nearly all the faculties' exam papers had been stolen.

A police source said the five individuals were caught in the act.

"Detectives from the Organised Crime Unit are investigating who was behind the theft and to whom the papers were to be sold," he said.

Unisa, according to its website, has more than 350000 students from throughout South Africa, Africa and elsewhere.

The university yesterday refused to say which exam papers had been stolen, how the theft took place, whether the exam papers were stored securely or if this was the first theft to be uncovered during this year's examinations.

Unisa spokesman Martin Ramotshela said the university was investigating.

"We will be able to provide details only once the investigation has been completed," he said.

"We view such transgressions in a serious light. When necessary, we will take disciplinary action. The university is confident that its actions to date will protect the integrity of Unisa examinations."

But a Unisa lecturer dismissed Ramotshela's assurances that the integrity of the examinations was protected, saying the breach could have serious consequences.

"This is being kept under wraps. None of the staff knows how severe the breach is, how many papers were stolen or how many faculties and subjects have been affected.

"One can only pray that the damage is limited," he said.

He said the exams would have to be reset. "This will be tedious, especially if it is for third, fourth and exit year students, because the setting and marking of exam papers involves external modulators."

Hawks spokesman Captain Paul Ramaloko confirmed the arrests and said the suspects had been charged with possession of stolen property.

"The suspects will appear in court soon," he said.

He said investigations were in the initial stages and that it was too early to say to whom the papers were being sold or for how much.