A high-security police building housing Interpol offices has been burgled again.

This brings to five the number of burglaries at the Pretoria building in the past three weeks.

At the weekend, thieves broke into the offices and stole laptops, electronic equipment and other devices from the Hawks anti-corruption unit.

The break-ins have raised fears about the security of classified information.

In one of the earlier incidents, burglars gained entry to the building using access-control cards and key codes and stole laptops, cameras and electronic equipment from the offices of five policemen seconded to Interpol.

No arrests have been made in that case.

Hawks spokesman Captain Paul Ramaloko confirmed the latest burglary: "The theft occurred at offices at the anti-corruption unit. At this stage it does not appear to be serious."

Police spokesman Lieutenant-General Solomon Makgale said they suspected a group was targeting the Pretoria offices specifically to steal laptops rather than to access the information on them.

But a crime intelligence source said the burglars appeared to be returning again and again because they were not finding the information they were looking for.

Makgale said some of the laptops stolen in the first burglary had been recovered from a pawn dealership.

"We suspect the people involved in the first burglary may be involved in the latest incident.

"Investigations are at an early stage. At this point we believe it is highly unlikely that those behind the burglaries are interested in the information contained on the laptops but are rather more interested in making quick cash.

"We have not yet ruled out the possibility of the involvement of people regularly visiting the building to do business with the police," Makgale said.

Police had not come across any evidence suggesting an inside job, he said.

A crime intelligence source close to the investigation said that in all the break-ins the burglars were believed to have used key codes and access cards to get into the building, targeting the offices of senior officers.

"It seems the criminals are not getting the information they are looking for and are resorting to raiding the whole building.

"They use the same modus operandi, coming back again and again to find what they are looking for. They are now going from floor to floor," the source said.

Unisa criminologist Rudolph Zinn said that regardless of the motive, the repeated breaches were of serious concern.

"It is not only the access that is being gained but the potential sensitive information that the stolen laptops might contain, be it on corrupt officers, international criminals, agents or informants."

He said one expected security at buildings housing specialised units to be extremely high, especially if they were at off-site premises.

"Most of these off-site premises are guarded by private security companies, who are not always up to scratch. One would naturally expect additional security measures to be taken, especially after more than one burglary at the same building."

Zinn said hard questions needed to be asked.

"If it this easy to break into this building multiple times one needs to ask what other unauthorised access has occurred, where items have not been stolen but where sensitive information has been accessed without anyone noticing.

"People need to be worried. The implications are huge. Interpol will be asking questions. These breaches bring into question what information the South African Interpol office staff will ultimately be allowed access to if these thefts continue."