Congressional investigators, in an undercover sting on the federal agency charged with protecting the U.S. from a radioactive attack, found out how easy it might be for terrorists to get their hands on the materials for a dirty bomb. Their radioactive material of choice? Americium-241, which is commonly used in certain kinds of construction equipment, called moisture-density gauges, and is "incredibly toxic," according to Daniel Hirsch, the president of the Committee to Bridge the Gap, a nuclear watchdog group. "Americium is a material very similar to plutonium," Hirsch told ABC News. "In fact, it’s about 50 times more toxic than plutonium gram for gram." Photos How Easy Is It to Buy the Materials for a Dirty Bomb? To start, the investigators set up a dummy construction company that in reality was no more than a mail drop in Martinsburg, W.Va. Twenty-eight days and no questions from the Nuclear Regulatory Commission later, the "company" received a license to legally buy certain quantities of Americium-241 and Cesium-137. "It was much too easy, much too easy, to get the licenses that would have allowed individuals setting up a dummy corporation to obtain enough material to create a dirty bomb," said Sen. Norm Coleman, R-Minn., who initiated the investigation in his role as ranking member of the Senate Permanent Subcommittee on Investigations. Dirty bombs are composed of a conventional explosives and radioactive material but don’t generate a nuclear explosion. Documents seized from al Qaeda operative Dhiren Barot, who was sentenced to life in prison in the U.K. last November, detail plans for a dirty bomb with Americium that would "maximize terror and chaos" in a series of coordinated attacks. The Nuclear Regulatory Commission says it regrets issuing the license without first checking out the buyer, but it stressed it doesn’t believe a radioactive dirty bomb is a significant threat. "If the effects are psychological and not real, we should not hype it," Edward McGaffigan, a member of the Nuclear Regulatory Commission since 1996, said. "Things nuclear get hyped, things chemical apparently do not." "The problem is that we live in a post 9-11 world," said Sen. Coleman. "The NRC, the Nuclear Regulatory Commission, has been operating in a post-1945 world." In congressional hearings slated for tomorrow, the Nuclear Regulatory Commission is expected to announce changes in its policy that would mandate one of its agents to personally visit the site of any company that wants to buy radioactive material to make sure they are legitimate. Do you have a tip for Brian Ross and the Investigative Team?