El Universal daily, quoting government sources, said Jose Antonio Acosta Hernandez -- also known as "El Diego" and reputed to be one of the bosses of the La Linea hitmen -- was captured in Ciudad Juarez on Friday.
The media reports said Acosta Hernandez was behind a cell phone-detonated car bomb that killed four people in Ciudad Juarez in July of 2010, the first attack of its kind in Mexico's drug war, and ordered the killing of at least a dozen more.
Formed by renegade police officers in the northern state of Chihuahua, La Linea act as enforcers for the Juarez cartel, a group based in the border city of Ciudad Juarez which controls some of the main drug trafficking routes into the United States.
The Mexican government had offered a 15 million peso reward for the capture of Acosta Hernandez, a former security chief who worked for a now-extinct Chihuahua state attorney's office, El Universal added.
A spokeswoman for the federal police in Mexico City on Saturday said she was aware an arrest was made but could not confirm it was Acosta Hernandez.
Since President Felipe Calderon sent the army to fight the drug cartels in late 2006, some 40,000 people have died.
In a separate statement late on Saturday, Mexico's Attorney General office said that Hector Guajardo Hernandez, a top drug trafficker for the Sinaloa cartel in the state of Baja California, escaped from custody on July 27.
Guajardo Hernandez, believed to be an ally of Mexico's most powerful drug lord Joaquin "El Chapo" Guzman, escaped from a Mexico City hospital where he was recovering from wounds he suffered during his May arrest.
(Reporting by Jean Luis Arce and Cyntia Barrera Diaz; Editing by Vicki Allen)