In performing its functions under the Convention, the United States Central Authority may, under such conditions as the Central Authority prescribes by regulation, but subject to subsection (c), receive from or transmit to any department, agency, or instrumentality of the Federal Government or of any State or foreign government, and receive from or transmit to any applicant, petitioner, or respondent, information necessary to locate a child or for the purpose of otherwise implementing the Convention with respect to a child, except that the United States Central Authority—

Whenever any department, agency, or instrumentality of the United States or of any State receives a request from the United States Central Authority for information authorized to be provided to such Central Authority under subsection (a), the head of such department, agency, or instrumentality shall promptly cause a search to be made of the files and records maintained by such department, agency, or instrumentality in order to determine whether the information requested is contained in any such files or records. If such search discloses the information requested, the head of such department, agency, or instrumentality shall immediately transmit such information to the United States Central Authority, except that any such information the disclosure of which—