The USGS has reported multiple aftershocks, including four with tremors measuring above 5.0 in magnitude.
According to Mexico's President Enrique Pena Nieto, this was the strongest natural disaster to hit the country in 100 years with violent tremors leaving Mexican homes and buildings in ruins, and thousands seeking safety.
Operation USA has ties to Mexico, having worked there in the wake of previous disasters, including the major 1985 quake and most recently following major flooding in 2013. The Mexican states of Chiapas, Oaxaca and Tabasco confirmed a number of deaths in their regions.
The news wire reported that at least 23 people were killed in Oaxaca, citing state Gov. Alejandro Murat. He urged people living near the coast to leave their homes as a protective measure.
Mexican quake biggest in century
According to the Associated Press, Juchitan, in the state of Oaxaca, was the worst-hit city, with several fatalities there.
Japan's weather agency has said quake-induced tsunamis may cause slight sea-level changes on Japan's Pacific coast early Saturday, with no damaging waves expected.
As a result of the quake, the Pacific Tsunami Warning Center warned of tsunami waves more than 10 feet high hitting some coasts of Mexico.
The devastation comes as at least 14 people have been killed by Hurricane Irma in the Gulf of Mexico.
Chiapas Governor, Manuel Velasco, said two women died on San Cristobal when a house and a wall collapsed. "I almost fell over", said Luis Carlos Briceno, an architect, 31, who was visiting Mexico City. "At first I laughed, but when the lights went out, I didn't know what to do", said Luis Carlos Briceno, an architect, who was visiting Mexico City.