A powerful earthquake has jolted Mexico City - measuring magnitude 7.1 according to the US Geological Survey (USGS) - causing buildings to sway sickeningly on the anniversary of a 1985 quake that did major damage to the capital.

Mexico's seismological agency estimated its preliminary magnitude at 6.8 and said its centre was east of the city in the state of Puebla. That municipality is about 40 miles southeast of the capital.

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Pictures fell from walls and objects were shaken off of flat surfaces. Some people dove for cover under desks.

A video that appear to show the earthquake in action show lights swaying above people crowding into hallways for safety, and then those lights seeming to lose power.

Mexico City earthquake in pictures Show all 13 1 /13 Mexico City earthquake in pictures Mexico City earthquake in pictures A handout picture provided by the citizen Edgar Cabalceta shows a general view of Mexico City following a magnitude 7.1 earthquake, in Mexico City, Mexico EPA Mexico City earthquake in pictures Rescuers and residents look for victims amid the ruins of a building knocked down by a magnitude 7.1 earthquake that jolted central Mexico damaging buildings, knocking out power and causing alarm throughout the capital on September 19, 2017 in Mexico City, Mexico. The earthquake comes 32 years after a magnitude-8.0 earthquake hit on September 19, 1985 Getty Images Mexico City earthquake in pictures A police officer stands guard near a building which collapsed after a quake rattled Mexico City RONALDO SCHEMIDT/AFP/Getty Images Mexico City earthquake in pictures Rescuers, firefighters, policemen, soldiers and volunteers remove rubble and debris from a flattened building in search of survivors after a powerful quake in Mexico City AFP/Getty Images Mexico City earthquake in pictures Rescuers and residents look for victims amid the ruins of a building knocked down by a magnitude 7.1 earthquake that jolted central Mexico damaging buildings, knocking out power and causing alarm throughout the capital on September 19, 2017 in Mexico City Getty Images Mexico City earthquake in pictures People try to rescue survivors from a collapsed buildings after a magnitude 7.1 earthquake on the Richter scale in Mexico City, Mexico, 19 September 2017. At least 79 people lost their lives in the states of Morelos, Puebla and Mexico by the earthquake of magnitude 7.1 on the Richter scale. EPA Mexico City earthquake in pictures People clear rubble after an earthquake hit Mexico City, Mexico REUTERS Mexico City earthquake in pictures People clear rubble after an earthquake hit Mexico City, Mexico REUTERS Mexico City earthquake in pictures Rescuers and residents assists an injured victim amid the ruins of a building knocked down by a magnitude 7.1 earthquake that jolted central Mexico damaging buildings, knocking out power and causing alarm throughout the capital on September 19, 2017 in Mexico City, Mexico. The earthquake comes 32 years after a magnitude-8.0 earthquake hit on September 19, 1985. Getty Images Mexico City earthquake in pictures People remove debris outside a collapsed building after an earthquake in Mexico City, Mexico REUTERS Mexico City earthquake in pictures People remove debris as they search for possible victims after a quake rattled Mexico City on September 19, 2017. A powerful earthquake shook Mexico City on Tuesday, causing panic among the megalopolis' 20 million inhabitants on the 32nd anniversary of a devastating 1985 quake. The US Geological Survey put the quake's magnitude at 7.1 while Mexico's Seismological Institute said it measured 6.8 on its scale. The institute said the quake's epicenter was seven kilometers west of Chiautla de Tapia, in the neighboring state of Puebla. AFP/Getty Images Mexico City earthquake in pictures A security guard walks over debris of a building which collapsed during a quake in Mexico City AFP/Getty Mexico City earthquake in pictures Reconstruction work in the towns affected by the telic movement has begun. Several temples suffered severe damage. Rex