Government nuclear experts are working undercover in major U.S. cities, using high-tech equipment hidden in briefcases and golf bags to hunt for radiological "dirty" bombs and other weapons terrorists might use.
The Energy Department's Nuclear Incident Response Teams were in Las Vegas, Los Angeles, New York and Washington last month, according to three government officials who spoke on condition of anonymity. Later, more teams went to other cities, which the officials declined to identify.
The Homeland Security Department also has sent detection equipment for police to use in Chicago, Detroit, Houston, San Diego, San Francisco and Seattle.
No specific threat
Agency spokesman Brian Roehrkasse said there is no specific intelligence pointing to a dirty bomb - which uses conventional explosives to disperse a plume of radioactive dust over several city blocks - or plots involving chemical, biological or nuclear devices.
The federal action came as the nation's terror alert status was upgraded just before Christmas to orange, or high risk. Security officials were particularly concerned that holiday gatherings with large crowds could serve as targets for terrorists.
The teams took readings ahead of New Year's celebrations at New York's Times Square and the Las Vegas strip, and for the Rose Bowl Parade on New Year's Day in the Los Angeles suburb of Pasadena, Calif.
The only detection of radiation so far was on Dec. 29 at a rented storage locker near downtown Las Vegas, one government official said. The White House was told, the FBI called in, and a robot was used to retrieve a duffel bag. In it was a stainless steel capsule of radium used for treating cancer.
A homeless man who provided the key to the locker told government officials he had found the capsule several years earlier. Officials said the man is not a terrorism suspect.
The nuclear experts, drawn from national labs, use detection equipment concealed in briefcases, golf bags and other items. Officials declined to provide specifics, but among the tools the experts might use is a Palm Pilot with a cadmium-zinc-telluride crystal that can detect radiation.
The government officials did not disclose how many experts are on the teams.
David Heyman, director of the homeland security program at the Center for Strategic and International Studies, a Washington think tank, said sending these experts to cities for unspecified threats is a new mission.
"Our teams are typically on call for accidents to react to possible incidences, but we're on new ground when we deploy them for countering unexpected threats," Heyman said.
Unlike a nuclear weapon, a dirty bomb has no atomic chain reaction and does not require highly enriched uranium or plutonium, which are normally heavily guarded and hard to obtain. It relies on a lower-grade isotope, like those used in medicine or research, for its radioactive component.
The al-Qaida terrorist network is known to have sought such a weapon, which experts say is most effective at spreading fear and panic but probably would not cause many casualties.
The Nuclear Regulatory Commission has said it receives an average of 300 reports a year of small amounts of radioactive materials missing from various users, but has no evidence that anyone is systematically collecting it to use in a dirty bomb.
Each year about 50 soil-testing gauges used for construction and road-building that contain small amounts of highly radioactive Cesium-137 and Americium-241 are reported stolen, and many are never recovered, the NRC has said. A dirty bomb could be made from the radioactive material, though it would take hundreds of the gauges to supply enough.
Commission spokesman Dave MacIntyre said there is no evidence the thefts are coordinated.