Guardian columnist Glenn Greenwald broke the story about the U.S. government's surveillance programs concerning data mining. / CBS News

RIO DE JANEIRO Two American journalists known for their investigations of the United States' government said Saturday they've teamed up to report on the National Security Agency's role in what they described as a U.S. assassination program.

Glenn Greenwald, the Rio-based journalist who has written stories about U.S. surveillance programs based on documents leaked by former NSA contractor Edward Snowden, is now working with Jeremy Scahill, a contributor to The Nation magazine and the New York Times best-selling author of "Dirty Wars."

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"The connections between war and surveillance are clear. I don't want to give too much away but Glenn and I are working on a project right now that has at its center how the National Security Agency plays a significant, central role on the U.S. assassination program," said Scahill, speaking to moviegoers in Rio de Janeiro, where the documentary based on his book made its Latin American debut at the Rio Film Festival.

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"There are so many stories that are yet to be published that we hope will produce 'actionable intelligence,' or information that ordinary citizens across the world can use to try to fight for change, to try to confront those in power," said Scahill.

"Dirty Wars" the film, directed by Richard Rowley, traces Scahill's investigations into the Joint Special Operations Command, or JSOC. The movie, which won a prize for cinematography at the Sundance Film Festival, follows Scahill as he hopscotches around the globe, from Afghanistan to Yemen to Somalia, talking to the families of people killed in the U.S. strikes.

Neither Scahill nor Greenwald, who also appeared at the film festival's question and answer panel, provided many details about their joint project or say when it would be finished.

http://www.cbsnews.com/8301-250_162-57605151/glenn-greenwald-working-on-new-nsa-revelations/