By John Ruwitch
BEICHUAN, China (Reuters) - China struggled to bury itsdead and help tens of thousands of injured and homeless onFriday when a powerful aftershock brought new havoc four daysafter an earthquake thought to have killed more than 50,000.
President Hu Jintao flew to the battered province ofSichuan and Premier Wen Jiabao said the quake damage couldexceed the devastating 1976 tremor in the north-eastern city ofTangshan that killed up to 300,000 people.
Wen called on officials to ensure social stability asfrustration and exhaustion grew among survivors, many of whomlost everything and were living in tents or in the open air.
China put the death toll at 21,500 on Friday but has saidit expects it to exceed 50,000.
Thousands of men, women and children were heading by footfor Mianyang, a city near the epicentre, saying they wereabandoning their ruined villages for good.
Anger has also focused on the state of school buildings,many of which crumpled in the quake, burying thousands ofchildren and prompting the Housing Ministry to order aninvestigation.
"If only there is the slightest hope, we will spare noeffort. If only there is one survivor in the debris, we willnever give up," Wen said over the debris of a collapsed schoolwhere hundreds were buried.
Thousands of residents from Beichuan, one of the areasworst hit by Monday's 7.9 magnitude quake, streamed down theroad away from the town, carrying babies, bags and suitcases asthey left in search of shelter.
A body lay covered on a makeshift stretcher by the side ofthe road, abandoned by someone unable to carry it further.Rocks the size of cars lay on the surface, evidence oflandslides triggered by the quake.
The town was a scene of devastation, with virtually everybuilding either demolished or damaged beyond habitation.
To the south, in the village of Houzhuang, residents saidthey were coping on their own, aid and troops yet to reachthem.
"We ate some corn, but now we are suffering from diarrhoeaafter drinking water from the ditch for two days," a residentsurnamed Liu said.
"Now we've been trying to get things out of the debris touse, like clothes, but we're very frightened that there will beanother earthquake, so we have to be very careful," he said.
BUCKLED ROADS, LANDSLIDES
The aftershock, measuring 5.9 on the Richter scale, hitLixian, to the west of the epicentre in Wenchuan, cutting offroads and newly repaired telecommunications.
"A number of vehicles were buried in landslides. Thecasualties were not known," Xinhua news agency said.
China has mobilised 130,000 army and paramilitary troops tothe disaster area, but with buckled and blocked roads, suppliesand rescuers have struggled to reach the worst-hit areas.
Neighbouring areas have also suffered, with more than50,000 made homeless in one county of Gansu province to thenorth, Xinhua said.
But there were still small victories.
Rescuers saved a child from the debris of a school inBeichuan 80 hours after the quake struck. They said they couldhear weak calls for help from amid the rubble, Xinhua said.
Three others in Beichuan were rescued on Friday, two in theremains of an office building and one in a collapsed hospital.
And 483 children and teachers escaped unscathed from awrecked school in Beichuan.
Many raised questions about school construction.
In Dujiangyan, a school collapse buried 900 students. InWufu, nearly every building in the village withstood the quakebut for a primary school, whose collapse killed about 300.
"Our child wasn't killed by the earthquake. She and theothers were killed by a derelict building. The officials knewit was unsafe," said Bi Kaiwei, whose daughter, 13, was killed.
Two girls held hands in the ruins of their school promisingnot to give up hope. "When rescuers found them, one in a comaand the other dead, their hands were still clenched together,"Xinhua said.
Housing Minister Jiang Weixin said the schools weren'tdesigned to withstand such a powerful earthquake, but addedcorruption was a possible cause.
"At this stage we cannot rule out the possibility thatthere has been shoddy work and inferior materials," Jiang tolda news conference in Beijing.
DAM THREAT
There were also concerns about epidemics if the dead werenot soon buried or cremated.
"We are in urgent need of body bags," Bai Licheng, aCommunist Party official in Sichuan's Yingxiu town, toldXinhua.
Bodies were lined up along the riverbank in the town, wheremore than 3,000 soldiers were searching for survivors.
The Ministry of Health issued a notice ordering bodies tobe cleaned where they were found and buried as soon aspossible, far from water sources and downwind from populatedareas.
Hundreds of damaged dams have also raised fears of collapseor flooding that could inundate towns and cities that arealready struggling to recover from the quake.
China has asked the United States for satellite images tohelp locate victims and identify damaged infrastructure.
In Sichuan and neighbouring Chongqing, reservoirs have beendamaged, some dams have cracked or are leaking water, andofficials have warned the full extent of the hazard was as yetunclear.
(Additional reporting by Emma Graham-Harrison in Yingxiu,Jason Li in Houzhuang; Writing by Nick Macfie; Editing by DavidFogarty)
