Mexico City ( CNN ) -- A strong 6.5-magnitude earthquake hit southern Mexico on Saturday night , killing two people and startling residents as far away as Mexico City , state media reported . It struck in Guerrero state at 7:47 p.m. local time , about 100 miles south-southwest of the capital , the U.S. Geological Survey said . The agency had previously put the quake 's magnitude at 6.7 . One person was killed when a rock fell on a vehicle , while another was crushed by a collapsed house , the state-run Notimex news agency reported , citing civil protection officials in Guerrero . At least 50 homes were damaged and at least four people were injured there , Notimex said . There were no immediate reports of major damage in the capital , but several areas were without power , Mexico City Mayor Marcelo Ebrard wrote on his Twitter page soon after the quake . Some startled residents in Mexico City ran out of their houses and into the streets . Loud sirens sounded after the quake , which had an estimated depth of 40 miles , the USGS said . Lorena Isla , a CNN iReporter in San Jeronimo Lidice , on the outskirts of Mexico City , took video of chandeliers swaying at her home . The side-to-side movement of the earthquake lasted about three minutes , said Isla , who lives on the third floor of a residence . `` This was the strongest one I ever felt , '' she said late Saturday . She took the video and rushed outside , where she said she fainted . `` Everybody is in panic , '' Isla said . Authorities urged residents to turn off natural gas devices . Some were having a hard time reaching relatives because of cell phone disruptions , according to Isla . CNN 's Jose Armijo and Phil Gast contributed to this report .
NEW : At least 50 homes are damaged , state media reports . One person was reportedly killed in a vehicle ; another crushed in a house . Mexico City 's mayor reports some blackouts , no major damage . The depth of the quake was 40 miles , the U.S. Geological Survey says .