If the owner fails to comply with an order, made pursuant to the provisions of N.H. Rev. Stat. § 48-A:3, to repair, alter, improve or to vacate and close the dwelling, or to remove or demolish the dwelling, the public agency may file a petition in the superior court in which it shall set forth the charges issued pursuant to N.H. Rev. Stat. § 48-A:3, II, as well as any other allegations bearing upon the unfitness of the dwelling for human habitation. The court shall thereupon direct notice to be given all parties having an interest in said dwelling, including mortgagees and persons in possession thereof. Such notice shall be given, where practicable, by personal service, except that if the person to be served resides outside the state, service may be made upon him by registered mail; and if there are any unascertained persons having an interest in said dwelling, notice may be given them by publication of the petition in a newspaper having general circulation in the municipality, such publication to be at least 10 days before the date set for the hearing. The court shall set a date for hearing such charges and additional allegations. Upon hearing, the matter shall be treated as de novo, and the court shall hear such pertinent evidence concerning the fitness of the dwelling for human habitation as may be relevant.