Homeland Security Department and other federal officials responsible for BioWatch, the nationwide system for detecting deadly biological attacks, have withheld key documents sought by a congressional committee, reports the Los Angeles Times. In a letter to Homeland Security Secretary Janet Napolitano, the committee chairmen call for her to comply with their original request for documents, which was triggered by a Times article that disclosed shortcomings in BioWatch's performance.

BioWatch was launched in 2003 by President Bush to "protect our people and our homeland." The Times reported in July that the system has generated scores of false alarms and, based on test results and computer modeling, could not be relied on to detect a germ attack. The false alarms — including the supposed detection of a deadly pathogen at the site of the 2008 Democratic National Convention in Denver — have caused tense, protracted deliberations among government officials responsible for deciding whether to order evacuations or other emergency actions. BioWatch operates in more than 30 major U.S. cities, where units placed atop buildings and other public places continuously suck air through composite filters. The filters are removed daily and delivered to public health laboratories, where technicians search for the DNA of anthrax, smallpox and a handful of other pathogens.