The Mexican president says his country has proof that illegal shipments of the powerful opioid drug fentanyl are arriving from China.
A container with hidden packages of the drug was intercepted in the Pacific port of Lázaro Cárdenas, President Andrés Manuel López Obrador said.
"We already have proof," he said, adding that he would ask the Chinese government to help stop the shipments.
US authorities say fentanyl is now the main driver of US drug overdose deaths.
In March President López Obrador said he had written to Chinese President Xi Jinping requesting Chinese help in the anti-narcotics fight, after US politicians had urged him to do so.
He told reporters on Friday that he would repeat that plea to Beijing: "In a very respectful manner, we are going to send this information to reiterate the request that they help us."
Mexican Navy Secretary Rafael Ojeda said the container intercepted in Lázaro Cárdenas had packages weighing 34-35kg (75 pounds) with traces of fentanyl and methamphetamine hidden in fuel resin. The cargo had left the Chinese city of Qingdao and passed through Busan in South Korea before reaching Mexico.
