A 49-year-old Mexican immigrant who was in Border Patrol custody died Monday, reportedly of a pre-existing heart condition. The man, who has not yet been identified, was detained on Sunday afternoon in southern Arizona. He was later taken to a hospital in Tucson, Arizona, where he was pronounced dead Monday morning. The man is the second immigrant to die while in U.S. custody this month. The first was an immigrant from Cameroon, who died under the custody of Immigration and Customs Enforcement. At least 11 other immigrants have died while in Customs and Border Protection custody so far this year.