Updated

Mexican marines on Thursday detained a young man they believe is one of the sons of Mexico's most-wanted drug kingpin, Joaquin "El Chapo" Guzman, leader of the powerful Sinaloa cartel.

The presumed son, identified by the Navy as Jesus Alfredo Guzman Salazar, was allegedly taking on an increasing leadership role in Mexico's most powerful drug cartel and purportedly served as the administrator of his father's fortune, estimated by Forbes magazine at about $1 billion.

The boyish, heavyset Guzman Salazar, known as "El Gordo," or "Fattie," was captured early Thursday during a raid by marines in Zapopan, an upscale suburb of the western city of Guadalajara, thanks to intelligence work and information from U.S. authorities, Navy spokesman Jose Luis Vergara said at a news conference.

Also captured in the raid was an alleged 19-year-old Sinaloa cartel member, Kevin Daniel Beltran Ríos. The pair were caught with a grenade launcher and four grenades, two assault rifles, two pistols and $135,000 in cash.

Vergara said Guzman Salazar was "a key element" in the Sinaloa cartel, "not just because of his blood tie to the leader ... but because he was presumably in charge of managing his assets."

"Intelligence sources say that Guzman Salazar was coordinating the majority of the drug shipments sent to the United States by the Sinaloa cartel, including cocaine and heroin," Vergara said, adding that "several sources also say Guzman Salazar was taking increasing control of Sinaloa cartel operations."

When he was paraded before news media, the paunchy Guzman Salazar mostly kept his eyes down or closed. Dressed in a red polo shirt and jeans, he did not answer when asked where his father is.

Vergara said the capture was due to months of Navy intelligence work and information from U.S. authorities. He said Guzman Salazar is wanted in the United States on an outstanding extradition request, to face charges in Chicago, Illinois related to drug trafficking.

Guzman Salazar and his father were indicted on multiple drug trafficking charges in the U.S. District Court for the Northern District of Illinois in August 2009, the U.S. Treasury Department said earlier this month, when it announced it had placed financial sanctions on Guzman Salazar and his mother, Maria Alejandrina Salazar Hernandez.

The designation bars American citizens from doing business with them and allows authorities to freeze their assets in the U.S.

U.S. authorities have said they believe "El Chapo" Guzman has at least six children with three women, including a woman whom he married in 2007 and who last year gave birth to twin girls in California. The Treasury Department described Salazar Hernandez, 53, as a wife of Guzman, without providing details.

A senior U.S. law enforcement official in Mexico who spoke on condition of anonymity for security reasons said that U.S. officials believe the younger Guzman "oversaw many of the drug transportation and money laundering operations ... (and) operated from Jalisco, Colima and Sinaloa" states.

In May, the department announced similar sanctions against Guzman's sons Ivan Archivaldo Guzman Salazar, 31, and Ovidio Guzman Lopez, 22.

Ivan Archivaldo Guzman Salazar, also known as "El Chapito," was also detained in Zapopan, in Jalisco state, on money laundering charges in Mexico in 2005, but was later released. Guzman Lopez plays a significant role in his father's drug trafficking activities, the department said.

"El Chapo" Guzman was put on the Treasury Department's list in 2001, the year he escaped from a maximum security prison hidden in a laundry truck. He has evaded authorities ever since, moving from hideout to hideout as he directs the operations of his cartel and a fight against rivals that has left thousands of people dead across Mexico.

The western state of Jalisco — where Guzman Salazar was arrested — as well as the nearby states of Colima, Nayarit and Sinaloa have seen a spike in drug-related killings in the last few years as the Sinaloa drug cartel battles its former allies in the Beltran Leyva cartel and its archrival the Zetas drug gang.

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Associated Press writers Katherine Corcoran and Mark Stevenson contributed to this report.