The action was based on a violation where the licensee did not secure from unauthorized removal or limit access to a Campbell Pacific Nuclear moisture/density gauge containing NRC-licensed material (nominally 10 millicuries (370 Mbq) of cesium-137 and nominally 50 millicuries (1850 Mbq) of americium-241 in sealed sources) at a construction site in Detroit, Michigan, an unrestricted area, nor did the licensee control and maintain constant surveillance of this licensed material.