Section 2. The head of a fire department in a city, town, or district wherein a fire or explosion has destroyed or damaged property shall investigate the cause and circumstances thereof in order to determine if such fire or explosion was caused by carelessness or design or shall cause such an investigation to be made by a member of the fire department of such city, town or district. They shall begin such investigation forthwith after such fire or explosion, and if it appears to the official making such investigation that the fire or explosion is of suspicious origin or is the result of a violation of law, or if he is unable to determine the cause, he shall immediately notify the marshal. All other fires or explosions by which a loss is sustained shall, within forty-eight hours, excluding Sundays and holidays, be reported in writing to the marshal. Reports required by this section shall be on forms furnished by the department, and shall contain a statement of all facts relating to the cause and origin of the fire or explosion that can be ascertained, the extent of damage thereof, the insurance upon the property damaged, and such other information as may be required. The marshal shall keep or cause to be kept a record of all fires or explosions occurring in the commonwealth, with the results of such investigations, and such records shall be open to public inspection.