How a key ingredient in Coca-Cola, M&M's is smuggled from war-torn Sudan

FILE - A farmer carries collected gum arabic from an Acacia tree in the western Sudanese town of El-Nahud that lies in the main farming state of North Kordofan Dec. 18, 2012. Gum arabic is seen on an Acacia tree in the western Sudanese town of El-Nahud that lies in the main farming state of North Kordofan Dec. 18, 2012.

Gum arabic, a vital ingredient used in everything from Coca-Cola to M&M's sweets, is increasingly being trafficked from rebel-held areas of war-torn Sudan, traders and industry sources say, complicating Western companies' efforts to insulate their supply chains from the conflict.