Bodies covered with sheets lined streets as rescue workers dug through schools and homes turned into rubble by China's worst earthquake in three decades in a desperate attempt to rescue victims trapped under concrete slabs. The official death toll rose Tuesday to nearly 12,000, and thousands remained buried or missing, the Associated Press reported. But hope that many survivors would be found was fleeting. Only 58 people were extricated from demolished buildings across the quake area so far, China Seismological Bureau spokesman Zhang Hongwei told the official Xinhua News Agency. In one county, 80 percent of the buildings had been destroyed. «Survivors can hold on for some time. Now it's not time to give up,» Wang Zhenyao, disaster relief division director at the Ministry of Civil Affairs, told reporters in Beijing. A day after the powerful 7.9 magnitude quake struck Monday afternoon, state media said rescue workers had reached the epicenter in Wenchuan county _ where the number of casualties was still unknown. The quake was centered just north of the Sichuan provincial capital Chengdu in central China, tearing into urban areas and mountain villages. Rain was impeding efforts and a group of paratroopers called off a rescue mission to the epicenter due to heavy storms, Xinhua reported. The death toll rose to 11,921, said Wang, most in Sichuan province. In Mianyang city alone near the epicenter, 3,629 people were dead and 18,645 were still buried in debris, Xinhua reported. At least 4,800 people also remained buried in Mianzhu, 60 miles (100 kilometers) from the epicenter, Xinhua said, citing local authorities. The Sichuan Daily newspaper reported on its Web site that there were more than 26,000 people with injuries and 9,400 thought to be buried in crushed buildings.