D.C. Code § 34-904: Inspection of books and examination of officers of utilities.

The Commission or any commissioner or any person or persons employed by the Commission for that purpose shall, upon demand, have the right to inspect the books, accounts, papers, records, and memoranda of any public utility, and to examine, under oath, any officer, agent, or employee of such public utility in relation to its business and affairs. Any person other than one of said commissioners who shall make such demand shall produce his authority to make such inspection or examination.