31 CFR §1010.850

1. (a)If a customs officer has reasonable cause to believe that there is a monetary instrument being transported without the filing of the report required by §§ 1010.340 and 1010.360 of this chapter, he may stop and search, without a search warrant, a vehicle, vessel, aircraft, or other conveyance, envelope or other container, or person entering or departing from the United States with respect to which or whom the officer reasonably believes is transporting such instrument.
2. (b)If the Secretary has reason to believe that currency or monetary instruments are in the process of transportation and with respect to which a report required under § 1010.340 has not been filed or contains material omissions or misstatements, he may apply to any court of competent jurisdiction for a search warrant. Upon a showing of probable cause, the court may issue a warrant authorizing the search of any or all of the following:
   1. (1)One or more designated persons.
   2. (2)One or more designated or described places or premises.
   3. (3)One or more designated or described letters, parcels, packages, or other physical objects.
   4. (4)One or more designated or described vehicles. Any application for a search warrant pursuant to this section shall be accompanied by allegations of fact supporting the application.
3. (c)This section is not in derogation of the authority of the Secretary under any other law or regulation.