DAKAR, May 9 (Xinhua) -- Eleven people were injured, four seriously, after a Boeing 737 passenger plane skidded off the runway during takeoff Thursday morning, Senegal's Blaise Diagne International Airport said in a statement. Air Senegal flight HC301, heading for Bamako, Mali, went off the runway during its takeoff phase at around 1:00 a.m. local time, the statement said. It said that among the 78 passengers on board, 11 people were injured, four seriously. An investigation is underway to establish the causes of the accident, the statement said. The airport has since been closed.