Rescuers hunted for survivors on Monday after a gas explosion tore through a high-rise residential building in central Russia, killing at least four people and leaving dozens unaccounted for. A large section of the building collapsed after the explosion around 6:00 am local time (1100 GMT) at the high-rise in the industrial city of Magnitogorsk, nearly 1,700 kilometres (1,050 miles) east of Moscow in the Ural mountains.