WASHINGTON (Reuters) - Undercover investigators, working for a fake firm, obtained a license to buy enough radioactive material to build a “dirty bomb,” amid little scrutiny from federal regulators, according to a government report obtained on Wednesday.

Personnel dressed in protective gear measure radioactivity in a file photo. Undercover investigators, working for a fake firm, obtained a license to buy enough radioactive material to build a "dirty bomb," amid little scrutiny from federal regulators, according to a government report obtained on Wednesday. REUTERS/Srdjan Zivulovic

The U.S. Nuclear Regulatory Commission issued the license to the dummy company in just 28 days with only a cursory review, the Government Accountability Office said in a report to be released on Thursday.

The GAO, which set up the sting, said the NRC approved the license after a couple of faxes and phones calls and then mailed it to the phony company’s headquarters -- a drop box at a United Parcel Service location.

“From the date of application to the issuance of the license, the entire process lasted 28 days,” the GAO said. “GAO investigators essentially obtained a valid materials license from the NRC without ever leaving their desks.”

The NRC oversees the U.S. nuclear industry and nuclear material safety issues.

The GAO report said its undercover agents made counterfeit copies of the license, changed the wording to remove restrictions on how much they were allowed to buy and then ordered enough radiological materials to build a dirty bomb.

The GAO, a nonpartisan investigative arm of Congress, said its investigators did not take possession of the radiological materials.

U.S. officials have warned that militant groups, including al Qaeda, could use conventional explosives and material from sources as common as hospital X-ray departments to build so-called dirty bombs that could spread radioactive waste across urban centers.

The GAO sting was requested by a Senate panel that has been exploring post-September 11 security gaps in the U.S. government’s regulation of radioactive material.

The senior Republican on the panel, Sen. Norm Coleman of Minnesota, said the panel found the NRC was issuing licenses for “dangerous” level materials before visiting facilities making the applications.

“The NRC’s first visit to the facilities could be up to one year after the license was issued. That’s like handing out a gun license and waiting a year to do the background check,” Coleman said in a statement.

The GAO recommended the NRC improve its process for examining license applications for radioactive materials and explore ways to prevent the counterfeiting of licenses.