If a township or city clerk has knowledge that there is a probable illegal or fraudulent registration in the township or city, or in any ward or precinct of the township or city, the clerk has the power and duty to make a full investigation of the facts concerning the registration and to ascertain whether any name has been illegally or fraudulently registered. A township or city clerk is authorized and empowered to call upon the police department of the city or the sheriff of the county in which the city is located, or both, to assist in making the investigation, and the police department and the sheriff are required to render assistance if the clerk makes a request for assistance, and to furnish the clerk at his or her request with all available assistance in making the investigation. A township or city clerk is further authorized and empowered if he or she considers it necessary or advisable to appoint assistant examiners for the purpose of the investigation. Bills for the services of the examiner must be approved by the clerk and must be audited and paid by the township board or legislative body of the city in the same manner as the expenses of conducting elections are paid.