The district court should enforce the Board's subpoena if the information sought is relevant to an investigation being conducted by the Board and is described with sufficient particularity. See NLRB v. G.H.R. Energy Corp., 707 F.2d 110, 113 (5th Cir. 1982); accord EEOC v. City of Norfolk Police Dep't, 45 F.3d 80, 82 (4th Cir. 1995) (noting that district court's review of administrative subpoena is limited to determining whether the agency is authorized to conduct the investigation, whether the agency "has complied with statutory requirements of due process," and whether the information sought is relevant). We, in turn, review the district court's decision to enforce the subpoena for abuse of discretion; we may reverse the district court's enforcement order "only in the most extraordinary of circumstances." G.H.R. Energy Corp., 707 F.2d at 113 (footnote omitted).