Mexican federal police have arrested the father-in-law of alleged drug lord Joaquin Guzman 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 on Tuesday.
Coronel is the father of Guzman's third wife, Ema Coronel Aispuro, who married the purported gang boss in 2007 in a mountainous town in Durango state.
The US 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".
Al Jazeera's Adam Raney, reporting from McAllen, Texas, near the Mexican border, said that Guzman is a "very big fish indeed" within the drug cartels.
"Chapo Guzman is Mexico's most-wanted man, and this man, Ines Coronel, is his father-in-law, and, according to the US goverment, one of the key operators in the Sinaloa cartel," said Raney.
Sanchez said officers arrested Coronel and the others at a warehouse and seized four automatic rifles, a handgun and more than 250kg 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 US Treasury Department levied financial sanctions against him.
Coronel's listing under the US Kingpin Act bars US citizens from having business transactions with him and allows authorities to freeze any assets he has in the United States.