The Immigration and Naturalization Service initiated deportation proceedings against Francisco Sanchez-Martinez in 1974, alleging that he was not a citizen of the United States. The Service contended that he was born in Imuris, Mexico, while Sanchez-Martinez contended that he was born in Nogales, Arizona. The Immigration Judge held that he was not a United States citizen, and the Board of Immigration Appeals affirmed. Sanchez-Martinez filed a petition for review with this court. We held that because he had made a non-frivolous claim to citizenship and had raised a genuine issue of material fact as to his place of birth, he was entitled to a de novo hearing in the district court on the question of citizenship. 8 U.S.C. § 1105a(a)(5).