Some of the world’s best known consumer electronics companies are examining their supply chains after discovering that tin from a mine controlled by renegade soldiers in the Democratic Republic of Congo is reaching international markets.

The Bisie mine, situated a day’s walk into the Walikale district of North Kivu, is the Congo’s biggest tin ore mine. It is controlled – in contravention of the country’s mining regulations – by the renegade 85th brigade of the Congolese army led by Colonel Samy Matumo.