Hagerstown, Md. ? A national strategy is needed for overseeing the expanding number of laboratories designed for research on the world’s deadliest pathogens, the Government Accountability Office said Monday.

Since the fatal anthrax attacks of 2001, the number of so-called high-containment labs has increased, but no federal agency knows whether their number meets or exceeds the national need or is at a level that can be operated safely, the GAO said in the 104-page document.

The federal watchdog agency recommended that the White House national security advisor, in consultation with the National Intelligence Council and the secretaries of health, agriculture, defense, and homeland security, identify a single entity to oversee the growth of high-containment labs.

The overseer would determine the number, location, and mission of the laboratories needed to effectively counter biological threats. It also would analyze the risks associated with the laboratories’ expansion and determine how much oversight is needed.

The agency would then develop national standards for designing, building, commissioning and operating the labs.

High-containment labs are rated either Biosafety Level 3 (BSL-3), for work with agents such as anthrax and tuberculosis bacteria that may cause serious illness or death if inhaled, or BSL-4, which is reserved for potentially lethal agents that lack vaccines or other treatments, such as the Marburg and Ebola viruses. Workers in BSL-4 labs must wear protective suits with a self-contained oxygen supply.

For most of the past 50 years, only two U.S. entities had BSL-4 labs: the Army biodefense center at Fort Detrick in Frederick, Md., and the Centers for Disease Control in Atlanta. Three more were built between 1990 and 2000, at Georgia State University in Atlanta; the University of Texas Medical Branch in Galveston, Texas; and the privately funded Southwest Foundation for Biomedical Research in San Antonio, Texas.

Since the 2001 anthrax mailings that killed five people and sickened 17 others, seven new BSL-4 facilities are in the works. Three will be at Fort Detrick, including a replacement for the existing lab there. The others will be in Manhattan, Kan.; Boston; Galveston, Texas; and Richmond, Va.

The GAO said no one knows how many BSL-3 labs exist or are planned, since only those that work with dangerous “select agents” must register with the CDC. The number of registered BSL-3 labs rose from 415 in 2004 to 1,362 by 2008, the GAO found.

The report comes on the eve of a Senate subcommittee hearing on biolab security, and a National Research Council review of health and safety risks at an Army biodefense lab under construction at Fort Detrick in Frederick.