In search of a terrorist nuclear bomb, the US federal government since 9/11 has run a far-reaching, top secret program to monitor radiation levels at over a hundred Muslim sites in the Washington, D.C., area, including mosques, homes, businesses, and warehouses, plus similar sites in at least five other cities, U.S. News has learned. In numerous cases, the monitoring required investigators to go on to the property under surveillance, although no search warrants or court orders were ever obtained, according to those with knowledge of the program. Some participants were threatened with loss of their jobs when they questioned the legality of the operation, according to these accounts. Federal officials familiar with the program maintain that warrants are unneeded for the kind of radiation sampling the operation entails, but some legal scholars disagree. News of the program comes in the wake of revelations last week that, after 9/11, the Bush White House approved electronic surveillance of U.S. targets by the National Security Agency without court orders. These and other developments suggest that the federal government`s domestic spying programs since 9/11 have been far broader than previously thought. The nuclear surveillance program began in early 2002 and has been run by the FBI and the Department of Energy`s Nuclear Emergency Support Team (NEST). Two individuals, who declined to be named because the program is highly classified, spoke to U.S. News because of their concerns about the legality of the program. At its peak, they say, the effort involved three vehicles in Washington, D.C., monitoring 120 sites per day, nearly all of them Muslim targets drawn up by the FBI. For some ten months, officials conducted daily monitoring, and they have resumed daily checks during periods of high threat. The program has also operated in at least five other cities when threat levels there have risen: Chicago, Detroit, Las Vegas, New York, and Seattle. FBI officials expressed concern that discussion of the program would expose sensitive methods used in counterterrorism. Although NEST staffers have demonstrated their techniques on national television as recently as October, U.S. News has omitted details of how the monitoring is conducted. Officials from four different agencies declined to respond on the record about the classified program: the FBI, Energy Department, Justice Department, and National Security Council. ”We don`t ever comment on deployments,” said Bryan Wilkes, a spokesman for DOE`s National Nuclear Security Administration, which manages NEST. In Washington, the sites monitored have included prominent mosques and office buildings in suburban Maryland and Virginia. One source close to the program said that participants ”were tasked on a daily and nightly basis,” and that FBI and Energy Department officials held regular meetings to update the monitoring list. ”The targets were almost all U.S. citizens,” says the source. ”A lot of us thought it was questionable, but people who complained nearly lost their jobs. We were told it was perfectly legal.” The question of search warrants is controversial, however. To ensure accurate readings, in up to 15 percent of the cases the monitoring needed to take place on private property, sources say, such as on mosque parking lots and private driveways. Government officials familiar with the program insist it is legal; warrants are unneeded for monitoring from public property, they say, as well as from publicly accessible driveways and parking lots. ”If a delivery man can access it, so can we,” says one. Most staff for the monitoring came from NEST, which draws from nearly 1,000 nuclear scientists and technicians based largely at the country`s national laboratories. For 30 years, NEST undercover teams have combed suspected sites looking for radioactive material, using high-tech detection gear fitted onto various aircraft, vehicles, and even backpacks and attaché cases. No dirty bombs or nuclear devices have ever been found - and that includes the post-9/11 program. ”There were a lot of false positives, and one or two were alarming,” says one source. ”But in the end we found nothing.” .