U.S. officials have secretly monitored radiation levels at Muslim sites, including mosques, offices, and private homes, since September 11, 2001 as part of a top secret program, U.S. News & World Report magazine said Friday. The magazine said on its website that the far-reaching program covered more than 100 sites in the Washington area and at least five other cities. According to the article, the effort involved three vehicles in the Washington area monitoring 120 sites a day, nearly all of them Muslim sites such as prominent mosques and office buildings selected by the Federal Bureau of Investigation (FBI). The program also operated in New York City, Chicago, Detroit, Seattle, and Las Vegas when threat levels there have risen. Vice President Dick Cheney was among those briefed on the monitoring program, the article said. "In numerous cases, the monitoring required investigators to go onto the property under surveillance, although no search warrants or court orders were ever obtained, according to those with knowledge of the program," the magazine wrote.