Four US citizens were kidnapped by armed men on 3 March while driving into the city of Matamoros in the north-eastern state of Tamaulipas, Mexico, across the border from Texas. The four were driving through Matamoros - a city of 500,000 located directly across the border from the Texas town of Brownsville - in a white minivan with North Carolina licence plates when unidentified gunmen opened fire, the FBI said this week. Medical tourism is common, particularly among people living in US border states