Police Minister Bheki Cele says Botswana nationals are well known for their expertise in the blasting of vans during cash-in-transit heists.
"We have discovered that there are foreign nationals among these guys. We have identified two Botswana guys and two Zimbabweans."
He said two Botswana nationals had been arrested.
"Botswana specialises in blasting, so I am sure they are working in the mines. They are brought for that kind of thing - their job is to blast these vans," Cele said.
Cele gave an update to the media on Operation Thunder, a police initiative which saw the deployment of 267 officers from the public order policing unit to nine stations in the Western Cape.
He said the success rate of cash-in-transit operations that rely on blowing up cash vans had been reduced following the arrests of more than 40 suspects in cash-in-transit robberies from June 4 to date.
"What is important is that the last almost five or six cash heists they failed at blasting, and people are asking why. It is because the police have reduced their skills [in] blasting because we have arrested their experts."
There have been 179 heists from January to date.