Whenever a county welfare agent receives an application for assistance under this chapter, an investigation and record shall promptly be made of the circumstances of the applicant to ascertain the facts supporting the application made under this chapter, and such other information as may be required by the rules of the state board. The county department and the state department shall have the power to conduct examinations, and the county board and such officers and employees as are designated by the state commissioner may also administer oaths and affirmation.