The Mekong River with its estimated 4,900 km in length flows through China, Burma, Laos, Thailand, Cambodia and Vietnam. This mighty stream has long been used as an important trading route and lifeline for the villagers alongside the river. The Shipping link between Yunnan, the southwestern province of China and Thailand was especially difficult due to rapids, shoals and reefs. Since the blastings of those, the Thai-Chinese trade has developed enormously. Most cargo boats belong to Chinese companies and ply between the port of Guan Lei in Yunnan and Chiang Saen in Thailand. Furthermore, the business with illicit drugs flourishes around the infamous Golden Triangle, the mountain regions of Myanmar, Laos and Thailand. The river section between Guan Lei and Chiang Saen ranks among the most dangerous of Mekong. Only in October 2011, two freighters were attacked and 13 sailors kidnapped and killed. In many cases drug smugglers are involved in these attacks. Since December 2011, the river passage has been controlled by Chinese patrol boats.