Mexican prosecutors say they have captured one of the Sinaloa cartel leaders who launched a struggle for control of the drugs gang after the re-arrest of Joaquin "El Chapo" Guzman.
The attorney general's office said it had detained a gang leader it called Damaso N, and a federal official confirmed it was Damaso Lopez.
He is believed to be locked in a dispute with Guzman's sons for control of the cartel's territories.
Guzman was extradited to the US earlier this year to face drug charges.`
Lopez, known by the nickname "El Licenciado" - a title for college graduates - was long considered Guzman's right-hand man and helped him escape from a Mexican prison in 2001.
With Guzman in jail, the Sinaloa cartel has been controlled by Ismael "El Mayo" Zambada Garcia and Rafael Caro Quintero, two of the most traditional, old-school capos, plus Lopez, and Guzman's son Ivan Archivaldo Guzman.
Joaquin Guzman faces drug trafficking, money laundering and other charges in the US. He has pleaded not guilty.