China struggled to bury the dead and help tens of thousands of injured, homeless and hungry on Friday, four days after a massive earthquake which is expected to have killed more than 50,000. President Hu Jintao flew to the battered province of Sichuan and Premier Wen Jiabao said the quake damage could exceed the devastating 1976 tremor in the northeastern city of Tangshan that killed up to 300,000 people. Wen called on officials to ensure social stability as frustration and exhaustion grew among survivors, many of whom lost everything and were living in tents or in the open air. Anger has also focused on the state of school buildings, many of which crumpled in the quake, burying hundreds of children and prompting the Housing Ministry to order an investigation. "If only there is the slightest hope, we will spare no effort. If only there is one survivor in the debris, we will never give up," Wen said over the debris of a collapsed school where hundreds were buried. In the village of Houzhuang, in the area worst hit by Monday's 7.9 magnitude quake, residents said they were coping on their own, with aid and troops yet to reach them. "We ate some corn, but now we are suffering from diarrhea after drinking water from the ditch for two days," said a Houzhuang resident surnamed Liu. He said more than 90 percent of the buildings in his village, in the hard-hit county of Anxian, were flattened. "Now we've been trying to get things out of the debris to use, like clothes, but we're very frightened that there will be another earthquake, so we have to be very careful," he said. China has mobilized 130,000 army and paramilitary troops to the disaster area, but the quake buckled roads and triggered mountain landslides, meaning that relief supplies and rescuers have struggled to reach the worst-hit areas. Many raised questions about school construction. In the town of Dujiangyan, a school collapse buried 900 students. In Wufu, nearly every building in the village withstood the quake but for a primary school, whose collapse killed some 300 students. "Our child wasn't killed by the earthquake. She and the others were killed by a derelict building. The officials knew it was unsafe," said Bi Kaiwei, whose 13-year-old daughter was among the dead.