(Adds comments from Mexican president on diplomat visit, paragraphs 6-8)
MEXICO CITY, July 12 (Reuters) - The U.S. Treasury Department on Wednesday imposed sanctions on 10 Mexican nationals and one company in the country for their alleged involvement in the Sinaloa Cartel's vast illicit fentanyl trafficking network.
The U.S. Treasury accuses the 10 people of links to suppliers of precursor chemicals used to make fentanyl, a highly addictive painkiller that has fueled the opioid crisis in the United States and a sharp uptick in overdose deaths.
Wednesday's additions to the Office of Foreign Assets Control (OFAC) sanctioned list include Noel Lopez Perez, the brother of Joaquin "El Chapo" Guzman's second wife, and Ricardo Paez Lopez, a cousin to the youngest of El Chapo's sons.
The sons, known as "Los Chapitos," are accused of leading a faction of the Sinaloa Cartel after their father's 2016 capture and extradition to the U.S. a year later. The fourth son, Ovidio Guzman Lopez, was captured in Mexico earlier this year.
The U.S. Treasury also sanctioned an import-export company, REI Compania Internacional, and its majority shareholder for allegedly receiving chemical shipments from China.
Mexican President Andres Manuel Lopez Obrador said after the Treasury announcement that the U.S. was acting "responsibly" in the fight against fentanyl and other drugs but that more needed to be done.
"It is necessary to attend the causes of the problem," he said during his regular morning news conference. "It's complex."
Lopez Obrador added that his Security Minister Rosa Icela Rodriguez would meet this month with U.S. Homeland Security adviser Elizabeth Sherwood-Randall to discuss the problem.
U.S. President Joe Biden's administration has been seeking increased cooperation from Mexico and China in stemming the flow of fentanyl and its precursor chemicals.
(Reporting by Kylie Madry; Additional reporting by Stefanie Eschenbacher and Raul Cortes; Editing by Sarah Morland, Mark Heinrich and Josie Kao)