OAKLAND, Calif. (KCBS) _ Attorney General Jerry Brown has announced a major takedown of key members of the Nuestra Familia gang, who he says have committed murder and other violent crimes orchestrated in prison by gang leaders using cell phones.

As part of the operation code-named “Street Sweeper,” a joint task force of 250 state and local law enforcement agents concluded a year-long series of arrests attacking the hierarchy of prison gangs.

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On Tuesday in Visalia and surrounding areas, agents arrested 34 gang members, including four gang leaders. Five other Nuestra Familia leaders were incarcerated in earlier operations.

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“Operation Street Sweeper represents a big step forward in reducing vicious street crimes orchestrated in prison by the Nuestra Familia hierarchy,” said Brown.

Brown said that three gang leaders serving life sentences direct Nuestra Familia activities from inside Pelican Bay’s Secure Housing Unit, also known as the “Shu,” where prisoners are isolated 24 hours a day.

He said gang leaders are able to direct gang members on the street through cell phones smuggled into the prison.

“In addition to arresting street gang leaders, we must cut imprisoned gang leaders’ ability to communicate with cell phones by blocking that communication through an electronic net over Pelican Bay,” said Brown.

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Technology is available that could jam cell phones, even selectively, within prisons, but federal laws would have to be changed to allow that to happen.