After the effective date of this chapter, and thereafter until the Governor finds and proclaims that an emergency no longer exists in preparing for the national defense, or whenever the United States is engaged in war, or whenever a war emergency has been declared to exist by the President of the United States, the Attorney General may appoint for the duration of the war or emergency, as the case may be, such additional special criminal investigators not to exceed nine in number as he deems necessary to carry out the provisions of this chapter. There shall not be more than 15 such investigators employed at any one time. The employment of such investigators shall terminate not later than 90 days after the conclusion of peace or the official termination of the emergency by the President or the Governor.