The earthquake occurred at 10:29 a.m. local time (11:29 a.m. ET), with an epicenter near El Coyul, 6.8 miles southwest of Santa María Zapotitlán in Oaxaca state.
The earthquake could be felt as far as Guatemala, Honduras and El Salvador. In capital Mexico City, approximately 190 miles north of El Coyul, tremors were felt and sirens were heard wailing.
The Pacific Tsunami Warning Center said that hazardous tsunami waves are possible within 1,000 kilometers of the epicenter, including along the coasts of Mexico, Honduras, Guatemala and El Salvador.
The damage in Oaxaca state is considered light to moderate according to the US Geological Survey (USGS) ShakeMap.
Estimates modeled by the USGS suggest that localized casualties and damage are possible but there are likely to be fewer than 100 fatalities and less than $100 million in damage. However, the model only includes earthquake shaking, and not any impacts from potential tsunamis on the coastline.
The civil protection in Oaxaca has not yet reported any major damage.
Earlier estimates put the magnitude of the earthquake at 7.7, but that has been revised down to 7.4 (and additional revisions are possible).
In 2017, two powerful earthquakes hit the country in two weeks, toppling buildings, cracking highways and killing hundreds of people. One had a magnitude of 7.1 and the other a magnitude of 8.1.
Mexico City is particularly vulnerable to earthquakes because its very soft and wet ground amplifies shaking and is prone to liquefaction, in which dirt transforms into a dense liquid when sufficiently churned.
This breaking story has been updated with additional reporting.