The Carletonville police say the crime happened on Friday, 3 June.
The six security guards on duty at Midas substation were doing routine patrols at the facility at approximately 22:30.
They noticed a large hole in the outside fence. When they investigated further, they saw some 15 men already in the facility.
The guards realised they were outnumbered and ran to their office. The suspects ran after the guards and caught up with them.
They grabbed the guards, tied them up and locked them in the office.
They cut the cables in the substation and fled with approximately R500,000 worth of wiring.
A case of business robbery was opened.
