WASHINGTON - Federal prosecutors in Arizona have opened a preliminary investigation of a camping trip Congressman Jim Kolbe, R-Ariz., took 10 years ago that included two teenage congressional pages, a Justice Department spokesman told NBC News. NBC News first reported on the camping and rafting trip on Tuesday. A spokesman for the Justice Department in Washington said that the U.S. attorney in Arizona has started a "preliminary assessment" of the trip, after an unidentified source made allegations about the congressman's behavior on the expedition.