Sasol...has been investigating a fire and hyrdofluoric gas leak at its Natref oil refinery near Johannesburg in which 17 people were injured...[In] a series of accidents at its plants since last June...at least 13 people have died...[Sasol's Chief Executive Pieter Cox stated] “Sasol takes responsibility for the accidents at the plants ... it is our obligation that when we bring in contractors we train them.” [also refers to DuPont, Total]