Every board of city service commissioners appointed under ss. 63.18 to 63.53 shall investigate the enforcement of ss. 63.18 to 63.53 and of its rules, adopted in accordance with ss. 63.18 to 63.53 to carry out the purposes of ss. 63.18 to 63.53 and the action of the examiners provided for in ss. 63.18 to 63.53, and the conduct and action of the appointees in the official service in its city, and may inquire as to the nature, tenure and compensation of all offices and places in the public service thereof. In the course of such investigation each commissioner may administer oaths, and the board may secure by its subpoena both the attendance and testimony of witnesses and the production of books and papers relevant to the investigation. The commission may investigate the character and standing in the community of all applicants for examination and appointment in the city service under ss. 63.18 to 63.53.