If a verified written complaint by or for a person claiming to be aggrieved by a practice prohibited by AS 23.40.110, or a written accusation that a person subject to AS 23.40.070 - 23.40.260 has engaged in a prohibited practice, is filed with the labor relations agency, it shall investigate the complaint or accusation. If it determines after the preliminary investigation that probable cause exists in support of the complaint or accusation, it shall try to eliminate the prohibited practice by informal methods of conference, conciliation, and persuasion. Nothing said or done during this endeavor may be used as evidence in a subsequent proceeding.