Mexican troops have said they have arrested the son of the country's most-wanted drug suspect, Joaquin "El Chapo" Guzman.
They said Jesus Alfredo Guzman Salazar was arrested with another person in central Jalisco state in an operation by marines in the city of Zapopan.
His father is the boss of the powerful Sinaloa cartel.
"El Chapo", or "Shorty", Guzman has been in hiding ever since he escaped from prison in 2001.
Jesus Guzman and the other detainee, Kevin Beltran Rios, also accused of belonging to the Sinaloa cartel, were transferred to Mexico City, and paraded in front of the media.
A spokesman for the Mexican Navy, Jose Luis Vergara, said Jesus Guzman - known as "El Gordo", or "The Fat One" - was a growing force within the organisation.
"He controlled most of the Sinaloa cartel's illegal drug trade between Mexico and the United States," he said.
Mr Vergara said Jesus Guzman also managed most of his fathers' properties. "El Chapo" Guzman appears on Forbes magazine's world billionaires list.
The BBC's Will Grant, in Mexico City, says that the net could be tightening around El Chapo, with several of his close allies arrested recently.
Experts say the Mexican authorities seem to be trying to hurt Guzman by targeting his family.
The same tactic was employed by the Colombian army to get to the notorious drug baron Pablo Escobar.
Jesus Guzman Salazar, 26, was indicted on drug trafficking charges in the US state of Illinois in 2009.
Earlier this month, the US treasury department imposed financial sanctions on him and his mother, Maria Alejandrina Salazar.
Last month, two other sons of Joaquin Guzman, Ivan and Ovidio, were also targeted by the treasury department. The measure means US citizens are not allowed to do business with them.
It is unclear whether Jesus Guzman Salazar will be tried in Mexico or extradited to the US.
With presidential elections due in Mexico on 1 July, President Felipe Calderon's war on drugs will be under scrutiny.
More than 55,000 people have died in Mexico in drug-related violence since he declared war on the cartels.
El Chapo was jailed in 1993, but escaped from his maximum-security prison in a laundry basket eight years later.
He heads the Sinaloa cartel, which controls much of the flow of cocaine, marijuana and methamphetamine to the United States.
The US state department has offered a reward of up to $5m (£3.2m) for information leading to his arrest.