Section 8. The marshal shall report to insurance companies, to owners of property, or to other persons interested in the subject matter of an investigation of the cause and circumstances of a fire any information obtained by such investigation which may in his opinion require attention from or by such insurance companies, owners of property or other persons. The fire commissioner of the city of Boston shall make like reports of fires investigated by him or by a person by him designated under section three. The marshal shall also report to the head of the fire department the results of any investigation into fires of suspicious origin reported to him by such head as required by section two.