The Civil Defense authorities in Madina are investigating what caused the collapse of an unfinished sewage canal in Madina that killed six workers. The incident took place on Jame'at Road, northwest of the city Saturday night. Two other workers were injured and are being treated at a hospital. According to Lt. Col. Talal Al-Harbi, Civil Defense spokesman, three rescue vehicles arrived at the scene of the incident in Al-Jurf District and managed to rescue two Pakistani workers. They later found the bodies of six other workers who were buried under the sandy soil at a depth of 10 meters. He said a committee from the Civil Defense is investigating the circumstances surrounding the incident.