MEXICO CITY — The three-story school structure had pancaked into a pile of concrete slabs. The bodies of 21 children and four adults had been pulled out. But still sounds came from the collapsed structure on Wednesday — and finally a survivor was located. Rescuers were struggling to free a girl who had been one of many trapped under the rubble of a Mexico City school that collapsed due to yesterday’s 7.1 magnitude earthquake. Images broadcast by Mexican media showed helmeted workers working at the debris at the Enrique Rebsamen school. Foro TV reported that rescuers spotted the child and shouted to her to move her hand if she could hear them, and she did.