Officials say that about 2.5 percent of China's elementary and middle school buildings are structurally unsound, and as many as 20 percent in one province are considered unsafe, according to a government official. School safety has become a major concern in China and an extremely sensitive political issue following May's massive earthquake in Sichuan province that killed 70,000 people. Many students died when their poorly built schools collapsed. Ministry of Education figures showed 20 percent of primary schools and 11 percent of middle schools in Yunnan, which borders Sichuan, "were not totally safe," the report said.