A. If, in undertaking such an investigation, the fire marshal or investigator appointed pursuant to § 27-56 makes an affidavit under oath that the origin or cause of any fire or explosion on any land, building, or vessel, or of any object is undetermined and that he has been refused admittance thereto, or is unable to gain permission to enter such land, building, or vessel, or to examine such object, within 15 days after the extinguishing of such, any magistrate serving the city or county where the land, building, vessel, or object is located may issue a fire investigation warrant to the fire marshal or investigator appointed pursuant to § 27-56 authorizing him to enter such land, building, vessel, or the premises upon which the object is located for the purpose of determining the origin and source of such fire or explosion. After issuing a warrant under this section, the magistrate shall file the affidavit in the manner prescribed by § 19.2-54. After executing the warrant, the fire marshal, or investigator appointed pursuant to § 27-56, shall return the warrant to the clerk of the circuit court of the city or county wherein the investigation was made.
B. If the fire marshal or investigator appointed pursuant to § 27-56, after gaining access to any land, building, vessel, or other premises pursuant to such a fire investigation warrant, has probable cause to believe that the burning or explosion was caused by any act constituting a criminal offense, he shall discontinue the investigation until a search warrant has been obtained pursuant to § 27-32.1, or consent to conduct the search has otherwise been given.