The truck had many passengers on board when it tipped over at Mutetenya village in Tanganyika province on Friday, DR Congo’s national police said on Twitter, Presstv Reported.
“All the cargo of cassiterite (a mineral source of tin) spilled down the steep slope,” it added, giving a provisional death toll of 22.
The truck had been travelling from the town of Manono to Lubumbashi, the mining capital of the country.
The truck “hit a big rock before rolling,” said Pierre Mukamba, the administrator of the mineral-rich Manono territory.
The vehicle is owned by the Mining Mineral Resources (MMR), an Indian company registered in Tanzania.
Deadly traffic accidents are common in the vast, poor central African country, where the mostly dirt roads are poorly maintained.
Lacking cars or public transport, many people jump on board long-haul cargo trucks in often risky conditions to travel across the country.