The 1985 Mexico City earthquake was a magnitude 8.1 earthquake that struck some states of Mexico and Mexico City on the early morning of 19 September 1985 at around 7:19 am (CST), caused the deaths of at least 10,000 people and serious damage to the Greater Mexico City Area. The complete seismic event consisted of four quakes. A pre-event quake of magnitude 5.2 occurred on 28 May 1985. The main and most powerful shock occurred 19 September, followed by two aftershocks: one on 20 September 1985 of magnitude 7.5 and the fourth occurring seven months later on 30 April 1986 of magnitude 7.0. The quakes were located off the Mexican Pacific coast, more than 350 kilometres (220 mi) away, but due to strength of the quake and the fact that Mexico City sits on an old lakebed, Mexico City suffered major damage. The event caused between three and four billion USD in damage as 412 buildings collapsed and another 3,124 were seriously damaged in the city. While the number is in dispute, the most-often cited number of deaths is an estimated 10,000 people but experts agreed that it could be up to 40,000.