N.Y. County Law § 209
The board of supervisors is empowered to conduct an investigation into any subject matter within its jurisdiction, including the conduct and performance of official duties of any officer or employee paid from county funds and the accounting for all money or property owned by or under the control of the county. The power to conduct investigations may be delegated to a committee of the board. The chairman of the board and any member of such committee may issue a subpoena requiring a person to attend before the board or such committee and be examined in reference to any matter within the scope of the investigation, and in a proper case to produce all books, records, papers and documents material or relevant to the investigation. A subpoena issued under this section shall be regulated by the civil practice law and rules. The chairman of the board and any member of such committee may administer the oath to any witness and adjournments may be taken from time to time.
N.Y. CountyLaw § 209