A self proclaimed enforcer for Mexican cartels has pleaded guilty to murdering nine people in California.

FOX News Radio's Jessica Rosenthal reports:

Jose Manuel Martinez was extradited to California while serving a prison term for murder in Alabama. A sheriff's captain there said he confessed to the murder and then the floodgates just opened.

Law enforcement says Martinez has admitted to killing over 30 people across the country, starting in 1980, for hire, on behalf of Mexican cartels. But prosecutors and police say he would not name his cartel associates.

Martinez initially pleaded not guilty to charges that he murdered nine people in Central California, but just as a preliminary hearing began during which prosecutors planned to present evidence of the murders to see if he should stand trial, he pleaded guilty.

Jessica Rosenthal, FOX News Radio.