Each special agent, supervisor of schools, or other official charged with the investigation of Indian agencies and schools, in the pursuit of his official duties shall have power to administer oaths and to examine on oath all officers and persons employed in the Indian Service, and all such other persons as may be deemed necessary and proper.
25 U.S. Code § 36 - Special agents and other officers to administer oaths
For transfer of functions of other officers, employees, and agencies of Department of the Interior, with certain exceptions, to Secretary of the Interior, with power to delegate, see Reorg. Plan No. 3 of 1950, §§ 1, 2, eff. May 24, 1950, 15 F.R. 3174, 64 Stat. 1262, set out in the Appendix to Title 5, Government Organization and Employees.