Can an administrative search be conducted without a warrant?

Administrative searches are "[a]mong the 'carefully defined classes of cases' for which no warrant is needed." See Karfeld v. United States, 944 F.2d 583, 586 (9th Cir. 1991). The administrative search exception authorizes limited warrantless searches of persons seeking entry to sensitive facilities where the search is "part of a general regulatory scheme in furtherance of an administrative purpose, rather than . . . to secure evidence of crime." Id. (quoting United States v. Davis, 482 F.2d 893, 908 (9th Cir. 1973)). Nonetheless, an administrative search must be reasonable under the Fourth Amendment. Id.