By Josue Gonzalez and Lizbeth Diaz
MEXICO CITY (Reuters) - Rescuers laboured against the odds on Thursday to extract survivors including school children and five Taiwanese factory workers trapped beneath collapsed buildings in central Mexico following the country's deadliest earthquake in 32 years.
More than 50 survivors have been plucked from disaster sites in Mexico City since Tuesday afternoon's 7.1-magnitude quake, and first responders, volunteers and spectators joined in chants of "Yes we can!"
The death toll was at least 233, revised down from 237 earlier on Thursday, according to Mexico's head of civil protection Luis Felipe Puente. In Mexico City 1,900 were injured.
As the chance of survival diminished with each passing hour, officials vowed to press on, heartened by a few success stories.
Late on Wednesday night, an 8-year-old girl was rescued from a collapsed building in the Tlalpan neighbourhood, nearly 36 hours after the quake, the Coyoacan neighbourhood government said on Twitter.
But the fight to save a 12-year-old girl at a collapsed school in the south of the capital faced difficulty. Navy-led rescuers have communicated with her but were still unable to dig her free.
Just as it seemed workers were going to save the girl, they had to suspend their work early on Thursday morning due to a debris collapse, local media reported.
Eleven other children were rescued from the same Enrique Rebsamen School, where students are aged roughly 6 to 15. Twenty-one children and four adults there were killed.
"There's a girl alive in there. We're pretty sure of that, but we still don't know how to get to her," Admiral Jose Luis Vergara told Televisa, whose cameras had special access to the scene to provide non-stop live coverage.
"The hours that have passed complicate the chances of finding alive or in good health the person who might be trapped," he said.
The Taiwanese Ministry of Foreign Affairs confirmed five nationals were trapped in a collapsed clothing factory in the Obrera neighbourhood. The victims included Taiwanese businessman Chen Po-wen, according to Carlos Liao, Taiwan's top envoy to Mexico.
Volunteers cutting through debris at the factory, which had been combed by rescue dogs, heard signs of life.
"First we heard blows, and then we established visual contact. There was a person trapped in a car," said rescue worker Amaury Perez. "We shouted: If you are inside the vehicle, please knock three times. He knocked three times."
Rescue workers were joined by crews from Panama, El Salvador, the United States and Israel with others from Latin American countries on the way.
Throughout the capital, crews were joined by volunteers and bystanders who used dogs, cameras, motion detectors and heat-seeking equipment to detect victims who may still be alive. Mechanical diggers moved large slabs of concrete.
OUTPOURING OF AID
Armed soldiers guarded abandoned buildings feared to be at the point of collapse. Some 52 buildings collapsed in Mexico City alone and more in the surrounding states.
Thousands of people have donated food, water, medicine, blankets and other basic items to help relief efforts. Companies provided free services, and restaurants delivered food to shelters where thousands of people have sought refuge after their homes were damaged.
President Enrique Pena Nieto, who has declared three days of national mourning, said, "If anything distinguishes Mexicans, it is our generosity and fraternity."
The extensive damage to many buildings, some of them relatively new, has raised questions over construction standards which were supposed to have improved after a devastating 1985 quake.
Tuesday's quake killed 102 people in Mexico City and the remainder in five surrounding states, officials said. The state of Puebla was hit hard. Governor Jose Antonio Gali said on local television that 86 churches had been damaged and more than 1,600 homes would have to be demolished.
The temblor came on the anniversary of the 1985 earthquake that killed thousands and still resonates in Mexico. Annual Sept. 19 earthquake drills were being held a few hours before the nation got rocked once again.
Mexico was still recovering from another powerful quake less than two weeks ago that killed nearly 100 people in the south of the country.
Parts of Mexico City, home to some 20 million people, are built on an ancient lake bed that trembles easily in a quake.
Some residents and volunteers voiced anger that emergency services and military were slow to arrive to poorer southern neighbourhoods of the city, and that wealthier districts appeared prioritised.
(Reporting by Adriana Barrera and Daniel Trotta; Additional reporting by Stefanie Eschenbacher and Veronica Gomez; Editing by Alistair Bell and Cynthia Osterman)