At least 10 residential buildings in Kolkata will be pulled down, a week after they partially collapsed during tunnelling for an underground rail line from Esplanade in the heart of the city to Kolkata's busiest railway station, Sealdah. "Water seepage had triggered land subsidence and it caused houses to collapse. Metro engineers put up sandbank and cement wall," Kolkata Metro Rail Corporation Managing Director Manas Sarkar said. "Another two-metre concrete wall is being constructed... 600 people had to be evacuated. The tunnel borer ran into an aquifer and the springs leaked," he said.