By Julia Symmes Cobb and Santiago LimachiCALI, Colombia, Aug 12 (Reuters) - Colombian rescue teams raced on Wednesday to find survivors still trapped ‌beneath collapsed buildings two days after a powerful earthquake left nearly ‌250 people dead. But ​he said large crowds of volunteers ‌and onlookers had at first made the search harder. Advertisement AdvertisementAdvertisement AdvertisementPolice had ‌imposed tighter controls around the site by ​Wednesday, while volunteers were being directed to specific ​tasks, helping rescuers work more ​effectively, he said. "We have been here since Monday waiting for the girl to be rescued, ​and for her grandparents ‌too," Perez said. (Reporting by ​Julia Symmes Cobb and Santiago Limachi in Cali, Colombia; Writing by ​Kylie Madry; Editing by Paul Simao)