Heavy snow yesterday made it necessary to close two mountain passes, one in Burgos and the other in Cantabria, and to use chains at 20 passes throughout half of northern Spain, three of which were on main highways. According to sources from the Civil Defence, the zones affected by snowfall were the autonomous communities of Catalonia - excepting Tarragona -, La Rioja, Navarra, the Basque Country, Cantabria, Asturias, Castilla and Leon, and the province of Huesca. The passes closed to traffic were those of Portillo de la Sia and Portillo de Lunada, both in Burgos, and Brañavieja in Cantabria. In the province of Leon, drivers needed chains to negotiate 13 mountain passes, two of which are situated on the national network, according to the DGT on its Internet page. These include those of San Glorio, La Magdalena, Monteviejo, San Isidro, Las Señales, and others. In the principality of Asturias, the eight passes affected by the snow include those of San Isidro, Tarna, Arnicio and Pajares. The use of chains was essential not only at these passes but also at the Bocos, La Mazorra and Carrales passes, all of which are in the province of Burgos. In Cantabria, it was only necessary to use chains for negotiating the Palombrera pass, whilst in Palencia the only pass which required chains was that of Piedraslenguas, according to the DGT web.