Traditional Buildings by the central government. The government's Agency for Cultural Affairs then provides guidance, advice, and funds for repairs and other work. Additional support is given in the form of preferential tax treatment. As of 1 February 2012, 93 Groups of Traditional Buildings have been nationally designated, with a further 1 designation at prefectural and 89 at municipal level. Buried Cultural Properties are Cultural Properties, such as tombs, caves, and ruins, which are buried into the ground. About 460,000 ruin locations are presently known to exist in Japan. The protective measures taken include restrictions on their excavation. Any investigative excavation and construction work in the vicinity of a known site requires a notification. If preservation of the site is impossible, developers are required to cover expenses necessary to carry out an excavation, record any data and preserve what is possible. In cases when charging these expenses is not possible, local public organizations carry out the investigation with public funds. Any object found under the ground must be given to police, except when its owner is known. The object is then investigated to determine if it qualifies as a Cultural Property. Any Cultural Property whose owner is not known becomes as a rule property of the prefecture. Conservation Techniques for Cultural Properties Techniques for the production of materials necessary for restoration and conservation, and the techniques of restoration and conservation themselves are not Cultural Properties, and are classified as Conservation Techniques for Cultural Properties. This form of protection was approved in 1975 (see below) and was made necessary by the disappearance of skilled craftsmen as a result of the industrialization. The techniques protected by the law applied to Tangible and Intangible Cultural Properties and included the mounting of paintings and calligraphy on scrolls, the repair of lacquerware and wooden sculptures, and the production of Noh masks, costumes and instruments. The minister of education can designate techniques indispensable for conservation as Selected Conservation Techniques. Examples of nominated entities in the field of architecture are the Japanese Association for Conservation of Architectural Monuments (for repairs and woodwork), the National Association for the Preservation of Roofing Techniques for Shrines and Temples (techniques for organic roofing materials: cypress bark, shingles, thatch) and the Association for the Conservation of Cultural Properties (paintings and lacquering of architectural monuments) In addition to the prestige associated with the nomination, the government provides subsidies for training, courses and documentation.