ELOXOCHITLAN, Mexico, July 5 (Reuters) - Mexican soldiers have dug out more than a dozen corpses after the side of a rain-soaked mountain collapsed on a bus carrying up to 60 passengers on a remote road. Troops using bulldozers and other heavy machinery pushed aside jagged boulders, dirt and fallen trees early on Thursday to reach the victims. After days of heavy rain, part of a steep mountain tumbled on the bus on Wednesday morning in an isolated area of the southern state of Puebla, burying it entirely under a sea of boulders and mud. The bus was thought to be carrying between 45 and 60 people. Relentless rain in recent days with the start of the annual rainy season has caused flooding in many parts of Mexico.