Mexico's government says it believes police have captured Vicente Carrillo, leader of the powerful Juarez drug cartel.
Monday, a spokesman for President Vicente Fox said a man believed to be Mr. Carrillo was arrested in a Mexico City shopping mall on Saturday.
Prosecutors are carrying out DNA tests to check the identity of the man, who reportedly has had extensive plastic surgery to change his appearance.
Vicente Carrillo Fuentes is the brother of former cartel leader Amado Carrillo, who died during a botched plastic surgery operation in 1997.
Drug-related violence in northern Mexico has soared in recent months as the Juarez cartel battles rival groups for control of the drug trade. Several of the groups have lost their leaders in a Mexican government crackdown President Fox has called the "mother of all battles" against drug trafficking.
Some information for this report provided by AP and Reuters.