Nigerian President Goodluck Ebele Jonathan has declared three days of national mourning after a Dana Airlines plane crashed in Lagos, the country's biggest city, in a heavily populated residential area, killing more than 150 people yesterday. According to officials, none of the 153 people on the 55-minute flight in the MD-83 plane survived the tragic crash. It has not yet been determined how many people on the ground were killed in the accident. The aviation department is looking into exactly what caused the crash as the plane attempted to land at Murtala Muhammed Airport. Some have said the plane hit a tree, others said power lines, while others said the pilot overshot the runway.