Mexico City ( CNN ) -- A strong 6.5-magnitude earthquake struck southern Mexico on Saturday night , about 100 miles south-southwest of the capital , the U.S. Geological Survey said . The quake , which hit at 7:47 p.m. local time , had an estimated depth of 40 miles , the USGS said . The agency earlier said it was 6.7 magnitude . 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 . No injuries were reported in the quake , located in Guerrero state . Some startled residents in Mexico City ran out of their houses and into the streets . Loud sirens sounded . CNN 's Jose Armigo contributed to this report .
NEW : Mexico City 's mayor reports some blackouts , no major damage . Comment: There were no immediate reports of injuries .