Ken Salazar, United States Ambassador to Mexico, says he hopes Mexico, China and the United States can work together to stop fentanyl trafficking after the US government charged four Chinese companies and eight Chinese individuals with trafficking in chemicals used in manufacturing fentanyl. It was the first time the United States has charged Chinese companies for trafficking fentanyl precursor chemicals inside the United States, rather than shipping them to Mexico, the origin of most of the fentanyl found in the country. IMAGES AND SOUNDBITES