In addition to the office of county detective, there is created in the office of the prosecutor, the office or position of county investigator which shall be in the unclassified service of the civil service. The prosecutor of each of the several counties of this State may appoint such number of suitable persons, not in excess of the number, and at salaries not less than the minimum amounts, in this act provided, to be known as county investigators, and to assist the prosecutor in the detection, apprehension, arrest and conviction of offenders against the law. Persons so appointed shall possess all the powers and rights and be subject to all the obligations of police officers, constables and special deputy sheriffs, in criminal matters.
Notwithstanding the provisions of this section, a single probationary or temporary appointment as a county investigator may be made for a total period not exceeding one year.