Mexican President Enrique Pena Nieto has declared three days of national mourning following Thursday's powerful earthquake that has killed at least 61 people.
"The power of this earthquake was devastating, but we are certain that the power of unity, the power of solidarity and the power of shared responsibility will be greater," Pena Nieto said in a televised address on Friday.
The US Geological Survey (USGS) reported the magnitude of the earthquake that hit southern Mexico late on Thursday as 8.1, but the president described it as an 8.2-magnitude quake - "the largest registered in [Mexico] in at least the past 100 years".
It was bigger than the one in 1985 that killed more than 10,000 people in Mexico City, he said. 
On Friday, police, soldiers and emergency workers raced to rescue survivors from the rubble of houses, churches and schools that were split down the middle.
Pena Nieto said that 61 people were killed, including 45 who died in Oaxaca state, 12 in Chiapas and four in Tabasco. More than 200 people were injured across Mexico, officials said.
The worst-hit city was Juchitan, on the narrow waist of Oaxaca known as the Isthmus, where 36 quake victims died.
About half of Juchitan's city hall collapsed in a pile of rubble and streets were littered with the debris of ruined houses.
On Friday, a crowd had formed outside the city hall, a Spanish colonial building where two policemen were trapped in the rubble.

Rescuers managed to extract one and were still working to save the other 18 hours after the quake.

"God, let him come out alive!" said a woman watching as four cranes and a fleet of trucks removed what remained of the building's crumbled wing.
A Police officer who had been working for days told AFP news agency that he could not remember an earthquake "this terrible".
"The whole city is a disaster zone right now. Lots of damages. Lots of deaths. I don't know how you can make sense of it. It's hard. My sister-in-law's husband died. His house fell on top of him."
A hospital also collapsed, Pena Nieto said after touring Juchitan and meeting with residents. The patients were relocated to other facilities.
The president said authorities were working to re-establish the supply of water and food and provide medical attention to those who need it. He vowed the government would help people rebuild and called for people to come together.