If, on expiry of the deadline set in the formal notice pursuant to article L. 1334-15, the owner or operator of the built property has not implemented the prescribed measures or has not had an expert report carried out to determine the necessary measures or to verify them, the representative of the State in the département may, in the event of a serious health hazard, suspend access to and the carrying out of any activity in the premises concerned and take any measures to restrict access to the premises until they are brought into compliance.