(A) It is the duty of the Chief or his or her agent in charge at any fire to make prompt and thorough investigation of the cause of the fire.
(1) For this purpose, he or she is authorized to request the Mayor to require the attendance of witnesses, and the production of books, papers, property, or other evidence, at a time and place deemed by the Mayor convenient and proper.
(2) Witnesses shall be required to give their evidence under oath, which shall be reduced to writing and placed on file with the Chief.
(B) A record of the proceedings shall be kept by the officers and shall be authenticated by the Chief or the assistant making the investigation.
(`81 Code, § 30.36)