It was a Monday that started out like any other for 10-year-old Li Yi.
The middle school girl was sitting in her classroom in Beichuan County in central China, unaware that in an instant her world would change, forever.
Eyewitness accounts say the school building rocked and shook violently before collapsing from the destructive force of a 7.9-strength earthquake.
Moments later, Li Yi awoke to find herself buried alive -- one of an estimated 20,000 people trapped in the debris of what once were thriving villages and towns.
More than 50 hours passed -- hours of torrential rain, cold, hunger and dusty air -- before rescuers stumbled upon her broken body.
Miraculously, they managed to pull Li Yi from the rubble, but not before amputating her left leg in the process.
The little girl's story was being played out countless times Thursday throughout the earthquake ravaged region, as rescuers raced against time to keep the death toll from climbing above 50,000.
Government officials issued a rare public appeal for rescue equipment, while workers feverishly cleared roads to improve access to the quake's epicenter.
Some Chinese officials admitted that despite rescue efforts, finding more stories like Li Yi's would be a "miracle."
"As the destruction was severe and people were buried somewhere deep below ground, there's real trouble," Zhang Zhoushu, vice director of the state-run China Earthquake Disaster Prevention Center, told the Times of London. "If there are some survivors under such conditions, it would be a matter of luck or a miracle."
Still, there were stories of survival that kept even faint hope alive.
In the devastated town of Dujiangyan in Sichuan, a 62-year-old man was saved following an all-night search through debris. Onlookers cheered and took photos with their cell phones, the Times of London reported.
And in Dujuangyan, a 22-year-old woman was pulled to safety after three nights, her rescue broadcast and cheered on state television.
"I was confident that you were coming to rescue me. I'm alive. I'm so happy," the unnamed woman said.
But, officials appeared Thursday to be shifting their relief efforts from search-and-rescue to body recovery.
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The confirmed death toll Thursday morning reached 19,509, up from the nearly 15,000 confirmed dead the day before, according to the Earthquake and Disaster Relief Headquarters of the State Council. The council said deaths could rise to 50,000, state TV reported.
More than 12,300 remained buried and another 102,100 were injured in Sichuan province alone, where the quake was centered, the vice governor told reporters.
In Luoshui town — on the road to an industrial zone in Shifang city where two chemical plants collapsed, burying hundreds of people — troops used a mechanical shovel to dig a pit on a hilltop to bury the dead. Two bodies wrapped in white sheets lay near the pit.
Police and militia in Dujiangyan pulverized rubble with cranes and backhoes while crews used shovels to pick around larger pieces of debris. On one side street, about a dozen bodies were laid on a sidewalk, while incense sticks placed in a pile of sand sent smoke into the air as a tribute and to dull the stench of death.
The bodies were later lifted onto a flatbed truck, joining some half-dozen corpses. Ambulances sped past, sirens wailing, filled with survivors. Workers asked the homeless to sign up for temporary housing, although it was unclear where they would live.
Experts said the time for rescues was growing short.
"Anyone buried in an earthquake can survive without water and food for three days," said Gu Linsheng, a researcher with Tsinghua University's Emergency Management Research Center. "After that, it's usually a miracle for anyone to survive."
More than 130,000 soldiers and police joined the relief operation, Xinhua said.
"This is only a beginning of this battle, and a long way lies ahead of us," Vice Health Minister Gao Qiang told reporters in Beijing. "For every thread of hope, our efforts will increase 100-fold. We will never give up."
Premier Wen Jiabao visited Qingchuan in northern Sichuan province, site of a collapsed school that buried dozens of children, to encourage doctors and nurses aiding the injured.
"The party and the government are grateful to you. The people need you," he said in footage shown on CCTV.
No outbreaks of disease had yet been reported, but relief workers were immunizing refugees against some illnesses, Gao said. Workers were seeking to ensure safety of drinking water and removing corpses to prevent the spread of bacteria.
Also Thursday, electricity supplies were restored to most parts of Sichuan for the first time since the quake, though Beichuan county near the epicenter remained blacked out, Xinhua said.
China also accepted an offer from Japan to send a rescue team, Foreign Ministry spokesman Qin Gang said in an announcement posted on the ministry Web site.
The International Federation of Red Cross and Red Crescent Societies issued an emergency appeal for medical help, food, water and tents.
Gu Qinghui, the federation's disaster management director for East Asia who visited Beichuan, said more than 4 million homes were shattered across the quake area.
"The whole county has been destroyed. Basically there is no Beichuan county anymore," Gu said in Beijing.
Roads were cleared Thursday to two key areas that felt the brunt of the quake's force, with workers making it to Wenchuan at the epicenter and also through to Beichuan county, Xinhua reported. Communication cables were also reconnected to Wenchuan.
Hundreds of troops marched to the epicenter across the Zipingpu dam that had reportedly suffered cracks from the disaster, raising fears it could endanger communities downriver. There was no repair work or extra security seen Thursday at the dam by an Associated Press photographer, indicating that the threat to the structure had likely passed.
Public donations so far have totaled $186 million in cash and goods, Xinhua said.
NBA star Yao Ming, China's most famous athlete, was planning to donate $285,000 to the relief effort, agent Erik Zhang said.
The Associated Press contributed to this report.