New York Consolidated Laws, General City Law - GCT § 6. Swearing witnesses

Whenever the common council of a city shall have appointed a committee of members of their body upon any subject or matter within the jurisdiction of such common council, or to examine any officer of the city, in relation to the discharge of his official duties, or to the receipt or disbursement by him of any moneys in the discharge of such duties, or concerning the possession or disposition by him, in his official capacity, of any property belonging to the city;  or to use, inspect or examine any book, account, voucher or document, in his possession or under his control as such officer, relating to the affairs or interests of such city, the chairman of such committee is authorized to administer oaths to all such witnesses as may appear or be brought before such committee.