A second earthquake has hit the Indonesian island of Sumatra where it is feared thousands of people died in an earlier quake.The country’s disaster agency say hundreds of houses have caved-in burying the occupants. Frantic rescuers have been digging casualties from the ruins but, it is feared, the number of dead is likely to keep on rising as time runs out for those still trapped in the rubble. The first 7.6 magnitude quake shook the city of Padang situated on one of the world’s most active fault lines. The second quake – magnitude 6.8 -was centred 150 kilometres northwest of Sumatra. The first quake caused panic. Schools were evacuated and people fled from built-up areas, headed for open ground. Padang’s main hospital is reported to have collapsed, roads have been cut off by landslides, broken water pipes have triggered flooding and severed power cables are causing sporadic fires. Sumatra is home to some of the country’s largest oil fields as well as its oldest natural gas terminal although there are no reports of any damage to these facilities. The first quake was felt as far away as Singapore, 440 kilometres to the north east, where high-rise office buildings were evacuated.