President Andres Manuel Lopez Obrador says communications with regions near the epicenter have been cut off, and the government is trying to get a clearer understanding of the situation.
Oaxaca state's governor reported a second death.
A powerful quake of magnitude 7.4 struck southern Mexico's Pacific coast on Tuesday, killing at least six people and cutting off isolated villages, as well as causing damage to buildings hundreds of miles away in Mexico City.
The quake caused buildings in Mexico City to sway and sent thousands of residents into the city's streets Tuesday.More news: Govt tells Patanjali to stop advertising COVID-19 meds 'Coronil' and 'Swasari'
The dead included a worker from state oil company Pemex, who suffered a bad fall, Mexico's civil protection agency said. Videos on social media showed water that apparently came from rooftop pools cascading down residential buildings.
The US Geological Survey reported that the quake struck with a magnitude of 7.4, at a depth of 23 kilometres.
In February 2018, a magnitude 7.2 struck 225 km to the northwest of this event that injured four people and damaged 1,000 homes in Oaxaca.More news: Counties in every state where COVID-19 cases are growing fastest
A powerful quake centered near Huatulco in southern Mexico was felt across the country, according to reports.
Helicopters flew over downtown Mexico City and police patrols sounded their sirens.
Mexico City Mayor Claudia Sheinbaum said power was knocked out in some areas.
Because oceanic crust is relatively dense, when the Pacific Ocean floor encounters the lighter continental crust of the Mexican landmass, the ocean floor is subducted beneath the North American plate creating the deep Middle American trench along Mexico's southern coast. It was shallow, only 26km below the earth's surface, which would have amplified the shaking. Mari González of the Princess Mayev hotel in Huatulco said staff and guests were able to evacuate the building before the quake, but that 45 minutes after the initial quake they were still outside as strong aftershocks continued.More news: Apex Legends mobile planned for release "by the end of the year"
Gonzalez said there was some visible broken glass and mirrors, but no major damage. Mexico city, the country's capital, is especially prone to earthquakes because it is situated on top of an ancient lake bed.