JOHANNESBURG (AFP) - Thieves broke into Interpol's offices in the South African capital twice at the weekend and stole computers with data that could compromise investigations into international crime, according to police and local media.

Police spokesman Solomon Makgale confirmed the weekend burglary at the International Police offices in Pretoria.

"We have registered a case of robbery," he told AFP in a text message, adding that "several laptops and other items" had been taken.

Police are investigating "the motive, the nature of the information contained in the laptops taken and who is behind the break-in," he said.

The criminals used access cards and key codes to enter the offices of three colonels and two captains on Saturday and Sunday, sources told local daily The Times.

The burglary seems suspicious because high-value items were left behind, according to the newspaper.

"In one of the offices, which was burgled twice, the thieves took a laptop and a tablet, but left another tablet and two R5 rifle magazines behind," a source told the newspaper.

There are fears the breach could jeopardise probes into Nigerian drug networks and Russian, Ukrainian and Chinese syndicates.

"Not everyone is happy with the investigations that are being done... there are police on the payroll of criminals and these criminals would love to have this information," another source told The Times.