At the time, the Metro had 101 stations, with 32 closed to the public in the weeks after the event. On Line 1, there was no service in stations Merced, Pino Suárez, Isabel la Católica, Salto del Agua, Balderas or Cuauhtémoc. On Line 2, there was no service between stations Bellas Artes and Tasqueña. On Line 3 only Juárez and Balderas were closed. Line 4 continued to operate normally. All of the closed stations were in the historic center area, with the exception of the stations of Line 2 south of Pino Suárez. These stations were located above the ground. The reason these stations were closed was not due to damage to the Metro proper, but rather because of surface rescue work and clearing of debris. Fourth stage (1985–1987) Fourth stage saw the completion of Line 6 from Instituto del Petróleo to its eastern terminal Martín Carrera and Line 7 to the north from Tacuba to El Rosario. Line 9 was the only new line built during this stage. It originally ran from Pantitlán to Centro Médico, and its expansion to Tacubaya was completed on 29 August 1988. For Line 9, a circular deep-bore tunnel and an elevated track were used. Fifth stage (1988–1994) For the first time, a service line of the Mexico City Metro ran into the State of Mexico: planned as one of more líneas alimentadoras (feeding lines to be named by letters, instead of numbers), line A was fully operational by its first inauguration on 12 August 1991. It runs from Pantitlán to La Paz, located in the municipality of the same name. This line was built almost entirely above ground, and to reduce the cost of maintenance, steel railway tracks and overhead lines were used instead of pneumatic traction, promoting the name metro férreo (steel-rail metro) as opposed to the previous eight lines that used pneumatic traction. The draft for Line 8 planned a correspondencia (transfer station) in Zócalo, namely the exact center of the city, but it was canceled due to possible damage to the colonial buildings and the Aztec ruins, so it was replanned and now it runs from Garibaldi, which is still downtown, to Constitución de 1917 in the southeast of the city. The construction of line 8 began in 1988 and was completed in 1994. With this, the length of the network increased , adding two lines and 29 more stations,