Police in Mexico say a cartel leader arrested last week has confessed to ordering the murder of 1500 people in the city of Juarez.
Jose Antonio Acosta Hernandez, 33, who is also known as 'El Diego', is suspected of being the leader of the La Linea gang, whose members work as hired killers for the Juarez cartel.
The cartel controls some of the main drug smuggling routes from Ciudad Juarez into the United States.
Police believe 'El Diego' was also behind a car bomb attack which killed four people in the border city.
He is also suspected of planning an attack on an American consulate worker and her husband last year.
The Mexican government had offered 15 million Mexican pesos ($US1,275,000) for information leading to his arrest.
The BBC reports Juarez is Mexico's most violent city, with more than 3000 murders in 2010.