Mexico waited anxiously on Thursday for signs of life in the rubble of collapsed buildings as a desperate search for survivors of a devastating earthquake entered a third day.
Authorities put the death toll following Tuesday's 7.1 magnitude quake at more than 250 people, with the number expected to rise.
Rescue workers scrabbled to remove tons of rubble at dozens of flattened buildings in the capital and across several central states.
But time is running out. Experts say the average survival time in such conditions and depending on injuries is 72 hours.
Authorities put the overall death toll at 272 -- 137 in Mexico City, 73 in Morelos state, 43 in Puebla, 13 in Mexico state, five in Guerrero and one in Oaxaca.
However, the situation on the ground was chaotic, and the figures were rising -- and sometimes falling.
Highlighting the confusion that still reigned two days after the quake, one story that gripped the world's attention turned out to be false: that of a girl supposedly trapped alive beneath the rubble of a school that collapsed in Mexico City.
Authorities denied Thursday that the girl existed.
"We have carried out a full count with the directors of the school and we are sure that all the children are either safe at home, in the hospital or unfortunately died," Angel Enrique Sarmiento, a top officer in the Mexican marines, told journalists at the ruins of the Enrique Rebsamen school on the capital's south side.
"There are indications there may be an (adult) still alive in the rubble. There are traces of blood, photographs, as if the person had dragged him or herself and may still be alive," he added.
Rescue workers had told journalists they were certain a girl was alive beneath the rubble, but the different versions of the story varied widely.
The story had made headlines around the world after the quake, injecting a ray of hope into a tragedy that killed 19 children and six adults at the school.
But real stories of hope continued to emerge from ruined buildings across the city, where more than 10,000 people lost their lives in a devastating earthquake in 1985.
In the north of the city, a man who had been trapped for 26 hours and a 90-year-old woman were pulled alive from the rubble.
Residents of San Gregorio in the tourist-magnet Xochimilco neighborhood in Mexico City's far south were angry at the lack of material aid and volunteers.
"I need volunteers! Yesterday everything arrived and now there is nobody. They come, they do some disaster tourism, and they leave," one volunteer who gave his name as Morales told AFP.
San Gregorio was badly hit by the quake with many collapsed buildings and others in a state of near-collapse.
Rescue teams were helped by thousands of ordinary civilians who dug through the rubble alongside them. Other Mexicans took to the streets with food and water for victims and emergency workers.
President Enrique Pena Nieto toured the hardest-hit areas and declared three days of national mourning.
"The priority remains saving lives," he said Wednesday night in a broadcast to a grieving nation, insisting there was still hope of finding survivors.
More than 50 people have been rescued from collapsed buildings in the capital, he said.
US President Donald Trump called Pena Nieto and offered assistance and search-and-rescue teams which were quickly being deployed, the White House said.
Rescue teams have flown in from Israel, El Salvador and Panama and more were expected from Ecuador, Honduras, Colombia and Spain.
Rescuers said the Israeli teams came with equipment enabling them to detect cell phone signals within the rubble.
The earthquake hit on the anniversary of a huge quake in 1985 that killed more than 10,000 people, the disaster-prone country's deadliest ever.
Tuesday's temblor struck just two hours after Mexico held a national earthquake drill, as it does every September 19 to remember the 1985 disaster.
A system of quake sensors was set up in 1993 along the Pacific coast, where tremors are more common.
People in Mexico City were not warned by it on Tuesday because the epicenter was only 120 kilometers (75 miles) outside the capital and thus outside the main area of sensor coverage, said Carlos Valdes of the National Center for Disaster Prevention.
Adding to the national sense of vulnerability, the earthquake struck just 12 days after another quake that killed nearly 100 people in southern Mexico.