Mexican federal police arrested the father-in-law of alleged drug lord Joaquin Guzman on Tuesday in a northern border city without any shots fired, authorities said.
Ines Coronel Barreras, 45, was detained in Agua Prieta, across the border from Douglas, Arizona, along with a 25-year-old son and three other men, Interior Deputy Secretary Eduardo Sanchez said.
Coronel is the father of Guzman's third wife, Emma Coronel Aispuro, who married the purported gang boss in 2007 in a mountainous town in Durango state, Sanchez said.
He said officers arrested Coronel and the others at a warehouse and seized four automatic rifles, a handgun and more than 550 pounds (250 kilograms) of marijuana.
Coronel was in charge of smuggling marijuana for the Sinaloa drug cartel across the Mexico-Arizona border, Sanchez said.
He said Mexican authorities began gathering intelligence on Coronel in January, the month when the U.S. Treasury Department levied financial sanctions against him.
The U.S. agency said at the time that Coronel "plays a key role" in the Sinaloa drug cartel led by Guzman, who is also known as "El Chapo."
Coronel's listing under the U.S. Kingpin Act bars U.S. citizens from having business transactions with him and allows authorities to freeze any assets he has in the United States.