Malaysia has called off the search for a 48-year old woman who fell into a sinkhole after nine days of painstaking efforts. What could have caused the 8-meter deep sinkhole in Kuala Lumpur that swallowed the Indian tourist on August 23? What should we know about sinkholes? Is Singapore less susceptible to sinkhole formation? Associate Professor Wu Wei from NTU School of Civil and Environmental Engineering explains what causes a sinkhole and the technologies that can mitigate sinkhole risks and damage.