Surigao - Philippine officials on Sunday warned survivors of a powerful earthquake that left at least eight people dead in the country's south to ensure their homes and buildings were sturdy enough before venturing back amid continuing aftershocks.A strong aftershock alarmed residents, some of whom screamed in fear, while waiting for President Rodrigo Duterte to arrive to console earthquake survivors gathered in a gymnasium in the hard-hit capital of Surigao del Norte province.The magnitude 6.7 quake struck late on Friday, killing at least eight people, injuring more than 200 and damaging the main provincial airport and about 1 000 houses in Surigao, officials said. Some residents said the shaking was so strong they could not stand up to rush out of their houses.Officials appealed for volunteer engineers to help check the stability of damaged schools, hospitals, malls, hotels and other buildings, especially in the provincial capital of Surigao city, which has been placed under a state of calamity to ensure a rapid release of emergency funds and prevent food hoarding. Power was restored to some parts of the city.Last for days"Our call is do not return hastily after the strong quake," said Romina Marasigan, spokesperson of the government's National Disaster Risk Reduction and Management Council. "We have to ensure that our residences are safe."The critical infrastructures — the schools, the hospitals and offices that provide services — should also be checked if they are still safe for use," she said. "We are again re-iterating our appeal for help from civil and structural engineers to ensure the safety of the people."Renato Solidum, who heads the Philippine Institute of Seismology and Volcanology, said at least 137 aftershocks had hit following the quake. "Aftershocks are normal after a strong earthquake. Typically, these may last for days, up to weeks," he said.Among the structures damaged by the quake were 12 schools, six bridges and some shopping malls, many of which had visible cracks, shattered glass windows and damaged canopies. The quake may have busted tap water pipes, limiting supply in Surigao city, which lies about 700km southeast of Manila and three outlying towns, officials said.