In what circumstances have courts interpreted "clear indication" or "probable cause" standards for body cavity searches at border searches?

In Rivas v. United States, 368 F.2d 703, 710-712 (9th Cir. 1966), cert. denied, 386 U.S. 945, 87 S.Ct. 980, 17 L.Ed. 2d 875 (1967), and Henderson v. United States, 390 F.2d 805 (9th Cir. 1967), while admitting the difficulty of defining such a "clear indication" standard precisely, we interpreted that language to mean that something less than "probable cause," yet more than "mere suspicion," is required to justify a body cavity search; and we held that rule to apply even to searches made at an international border.