South Africa’s state-owned rail network operator, Transnet SOC Ltd., has hired five private security companies in an effort to reduce chronic theft and vandalism of trains that disrupt its operations.

Transnet said it was responding to changing criminal trends through the plan, which holds the security service providers liable for protecting its freight rail operations, according to a statement Wednesday.

There were more than 4,800 cases of cable theft last year across Transnet’s operations with a conviction rate of only 4%, Chief Executive Officer Portia Derby said at a Bloomberg event in Johannesburg last week. Criminals target the copper contained in cables, disabling electric trains that account for most of the fleet.

The disruptions, along with other failures that have idled locomotives, have cost miners tens of billions of dollars because they’ve struggled to move coal and other products to export harbors. Trucks have taken up the deliveries along some routes, creating safety issues and tearing up roads that weren’t designed to handle such traffic. 

“Service providers will enforce a mix of physical guarding, armed response teams, and interventions to address organized crime groupings behind the illicit copper market,” Transnet said. There have been protests at Transnet sites by employees of security firms previously hired by the company, some of whom failed a vetting process to be retained under the new arrangement, it said.