N.Y.C. Charter § 805: Section 805. Conduct of investigations.

a. For the purpose of ascertaining facts in connection with any study or investigation authorized by this chapter, the commissioner and each deputy shall have full power to compel the attendance of witnesses, to administer oaths and to examine such persons as he may deem necessary.

b. The commissioner or any agent or employee of the department duly designated in writing by him for such purposes may administer oaths or affirmations, examine witnesses in public or private hearing, receive evidence and preside at or conduct any such study or investigation.