 Trenes de Buenos Aires, Ferrocentral, Ferrobaires, and Tren Patagónico were some of the private companies that managed Argentina's long distance passenger rail network in this period.More recently, the government has begun nationalising some of these private companies or simply not renewing their contracts, while at the same time, the state-owned Trenes Argentinos began re-opening services and improving on the once private services using completely new rolling stock, including services from Buenos Aires to Mar del Plata and Buenos Aires-Rosario-Cordoba.In many cases, the Argentine Government has completely replaced, or is in the process of replacing, the existing infrastructure with continuous welded rails on concrete sleepers.