Is a search for illegal aliens permitted at a border search?

The language in Carroll v. United States, supra, 267 U.S. at 154, 45 S.Ct. at 285, upon which the "border search" doctrine is based, indicates that for this purpose a search for aliens is indistinguishable from a search for merchandise: "Travelers may be so stopped in crossing an international boundary because of national self-protection reasonably requiring one entering the country to identify himself as entitled to come in, and his belongings as effects which may be lawfully brought in" (emphasis added).