An explosion and fire at a Qatari natural gas site left 13 people dead and 66 injured on Sunday, according to the country’s energy minister.

Saad Sherida al Kaabi, Qatar’s energy minister and the CEO of QatarEnergy, confirmed on Monday morning that the operations incident was an accident. The incident occurred when workers were restarting operations at the Barzan plant, which had been shut down since December, in the major industrial area of Ras Laffan.