The South African Police Service told Reuters that the matter was being investigated, but declined to give further details.
COPPER PRICES HIT AN ALL-TIME HIGH ABOVE $10,700 A TONNE IN MAY
Glencore declined to comment. Trafigura said it did not comment on security issues. Traxys did not respond to requests for comment.
Copper mined in Zambia and Congo, which accounts for about 10% of global supplies estimated at 24 million tonnes, is transported to ports across southern Africa.
A total of 66 trucks carrying copper were robbed between January and May this year, and 60% of the hijackings occurred in South Africa, one of the sources said.
With the average truck carrying between 32 and 34 tonnes of copper cathode, the thefts would amount to roughly $21 million worth of copper at current prices.
More trucks were stolen in June and July, according to the source, who did not provide figures for those months but said one truckload of the copper stolen on July 9 was worth $470,000.
Organised crime gangs melt down copper to remove serial numbers and other marks of ownership, and then resell it locally or transport it by truck to be sold in neighbouring countries, two sources said.
Copper prices hit an all-time high above $10,700 a tonne in May thanks to a rebound in global demand, including in top consumer China, as manufacturing activity ramped up and economies reopened after covid-19 lockdowns.