WASHINGTON  - Most European air force bases that house US nuclear bombs are failing to meet security requirements to protect the weapons, according to an internal US Air Force investigation. The air bases often fall short of US Defense Department (DOD) standards, with fencing, lighting and buildings in need of repair and security guards lacking sufficient training and experience, said the document, obtained by the Federation of American Scientists (FAS). The 30-member air force team looking at the safety of nuclear weapons said that "inconsistencies in personnel, facilities, and equipment provided to the security mission by the host nation were evident as the team traveled from site to site" in Europe. "A consistently noted theme throughout the visits was that most sites require significant additional resources to meet DOD security requirements," said the report, titled "Air Force Blue Ribbon Review of Nuclear Weapons Policies and Procedures." At some bases, military conscripts with less than a year of active duty experience were assigned the task of guarding the weapons against theft, the report said. As a result of the security concerns, the United States may decide to consolidate the nuclear weapons at fewer bases in Europe, according to Hans Kristensen, who posted the results of the investigation on his blog on the FAS website. Consolidating the storage of the weapons would "minimize variances and reduce vulnerabilities at overseas locations," said the report. Several hundred thermonuclear bombs, about 200 to 350 B-61 bombs according to unofficial estimates, are kept at air bases in six NATO countries, including at four national air bases in Belgium, Germany, Holland and Italy. A summary of the same report released in February had exposed a major nuclear safety breach in which a B-52 bomber was allowed to carry six live nuclear warheads across the United States last year without approval from military officers. The revelation led to the resignations of the top military and civilian leaders at the US Air Force. The partially declassified version of the report showed that security concerns over weapons stored in Europe were much greater than previously known, Kristensen wrote. The B-61 bombs could not be detonated if stolen because of locks on the devices, Time magazine reported. But the weapons-grade nuclear material could be removed and used to create a "dirty bomb," it said.