The day after Monday's earthquake saw the spotlight in China turning on relief and rescue operations, even as the extent of the damage wrought by the 7.9 magnitude quake gradually became clearer. More than 12,000 persons were estimated to be dead in Sichuan Province alone and thousands missing or buried. China's worst earthquake in three decades devastated small cities and towns in the hills north of Chengdu, Sichuan's capital. Large portions of these areas were flattened, with more than 3.46 million houses collapsing, said Sichuan's Vice-Governor Li Chengyun. Among other buildings, several schools and chemical plants crumbled, trapping many persons under mounds of concrete, bricks and soil. In Mianyang, near the epicentre, 3,629 persons were dead and 18,645 were still buried in debris according to Xinhua news agency. At least 4,800 remained buried in Mianzhu, 100 km from the epicentre. Two chemical factories in Shifang city were destroyed, spilling 80 tonnes of toxic liquid ammonia and forcing 6,000 persons to evacuate. Six hundred were reported dead in the city. Amongst the casualties, schoolchildren formed a high proportion, given that Monday's quake had struck in the afternoon while classes were ongoing. Just east of the epicentre, 1,000 students and teachers were killed or missing at a collapsed high school in Beichuan County, where a six-storey high building collapsed. These deaths were separate from those that occurred at another school in Dujiangyan, where 900 students were buried, the majority feared dead. Search and rescue operations were in high-gear on Tuesday, with the Chinese Premier Wen Jiabao personally directing the efforts. As of Tuesday noon, the government had allocated 360 million Yuan ($52.17 million) for disaster relief. More than 50,000 soldiers from the People's Liberation Army were sent to the affected areas, as were thousands of medical workers and rescue specialists from around the country. Rescue efforts were, however, hampered by bad weather. Heavy rain, landslips and thick clouds made it difficult for troops to reach mountainous areas at the heart of the quake. Wenchuan County, the epicentre, remained totally cut-off for almost 24 hours after the quake first struck and was finally breached by relief workers around lunch-time on Tuesday. While figures for casualties from Wenchuan, a county with a population of 1,12,000, were still not available, 15 missing British tourists were believed to have been in that area. They were likely visiting the Wolong Nature Reserve, home to more than 100 endangered giant pandas, whose fate was also not known. The animals themselves were reported as unharmed . Aftershocks, some measuring as high as 6 on the Richter Scale, continued to jolt Sichuan throughout Tuesday. Those in the affected areas are reportedly sleeping in makeshift tents. Monday's quake was the deadliest in China since the 1976 quake that struck Tangshan city, east of Beijing. The quake killed 2,40,000 persons.