In towns such as Juchitan, in the state of Oaxaca, people were afraid to return to their homes, fearing the effects of hundreds of aftershocks striking the area.
Juana Luis, 40, spent the night with her family under a tree in the garden next to their house, which was reduced to a pile of concrete rubble, twisted metal and electrical cables.
"It is very sad to live like this, on hammocks hung in the garden, under the rain, with our belongings buried in the house," she said.
She said she went out to get emergency food handouts from authorities - competing with other harried locals - and managed to get a box of beans, rice and other essentials.
Food prices have soared in the disaster zone since the quake struck.
As soldiers and mechanical diggers worked to clear the ruins of the town hall, families in poorer districts picked through the rubble of their houses and gathered to cook on a fire in the open.
"We still have no water or electricity. We are sleeping with the children out here in the open," said Maria de los Angeles Orozco, one of the locals gathered in the town's Martes Santo Square.
"No-one has come to help us."
No-one has come
Authorities put the overall toll from Thursday night's quake at 65, all in the states of Oaxaca, Tabasco and Chiapas.
The federal government said it was investigating claims by an official in Oaxaca that 25 more people had been found dead there.
"We still have to confirm that," federal urban development secretary Rosario Robles said on television channel Milenio.
Rescuers were still searching for victims in remote, mountainous districts that are home to isolated communities.
Mexican seismological authorities measured the quake at magnitude 8.2, making it bigger in magnitude even than the 8.1 quake that killed 10 000 people in Mexico City in 1985.