Rescuers laboured against the odds into the dawn on Thursday to save a 12-year-old schoolgirl and untold other survivors who may be trapped beneath crumpled buildings in central Mexico after the country’s deadliest earthquake in 32 years.

More than 50 survivors have been plucked from several disaster sites since Tuesday afternoon’s 7.1-magnitude quake, leading to impassioned choruses of “Yes we can” from the first responders, volunteers and spectators gathered around the ruins.

At least 237 others have died and 1,900 were injured.

As the odds of survival lengthened with each passing hour, officials vowed to continue with search-and-rescue efforts such as the one at a collapsed school in southern Mexico City, where navy-led rescuers could communicate with the 12-year-old girl but were still unable to set her free.

Eleven other children were rescued from the Enrique Rebsamen School, where the students are aged roughly six to 15, but 21 students and four adults there were killed – 15 hours into the effort, Admiral Jose Luis Vergara said rescuers still could not pinpoint her location.

“There’s a girl alive in there, we’re pretty sure of that, but we still don’t know how to get to her,” said Vergara.

“The hours that have passed complicate the chances of finding alive or in good health the person who might be trapped,” he said.

Rescuers periodically demanded “total silence” from bystanders, who would freeze in place and stay quiet to better hear any calls for help.

As with other disaster sites throughout central Mexico, officials dared not employ heavy lifting equipment for fear of crushing anyone below.

Rescue mission

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. Some 52 buildings collapsed in Mexico City alone and more in the surrounding states.

The quake killed 102 people in Mexico City and the remaining 135 from five surrounding states, officials said late on Wednesday.

At least nine Latin American countries pledged to rush in search-and-rescue teams or technical assistance, with crews from Panama and El Salvador already on the job, as did the United States, Spain, Japan and Israel.

Mexico was still recovering from another powerful quake less than two weeks ago that killed nearly 100 people in the south of the country.

The epicenter was a mere 31 km (32 miles) beneath the surface, sending major shockwaves through the metropolitan area of some 20 million people. Much of the capital is built upon an ancient lake bed that shakes like jelly during a quake.