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.