Section 16. There shall be in the office of the state auditor a bureau of special investigations, headed by a director, who shall be appointed by the state auditor, and who shall be a person of ability and experience and shall devote his entire time to the duties of the office. Said auditor may appoint such other experts and officers as he deems necessary to carry out the work of the bureau. Employees of the bureau shall not be members of a collective bargaining unit. The director may expend, subject to appropriation, for legal, investigative, clerical and other assistance and expenses such sums as may be available therefor by the general court. Nothing in this section shall be construed as extending the audit authority of the auditor.