The specified fire inspector has the powers of a trial judge for the purpose of summoning and compelling the attendance of witnesses before him to testify in relation to any matter which is, by the provisions of Section 11-9-1, a subject of investigation. The fire inspector may also administer oaths and affirmations to persons appearing as witnesses before him. False swearing in any matter or proceeding provided for in Sections 11-9-1 and 11-9-2 is perjury and shall be punished as such. The fire inspector and his subordinates have authority at all times of the day or night, in the performance of the duties imposed by the provisions of Sections 11-9-1 and 11-9-2, to examine any building or premises where a fire has occurred and adjoining and nearby buildings and premises. All investigations held by or under the direction of the fire inspector may be private, in his discretion. Persons other than those required to be present by the provisions of Sections 11-9-1 and 11-9-2 may be excluded from the place where the investigation is held, and the witnesses may be kept apart from each other and not allowed to communicate with each other until they have been examined.