Around 2:30 pm, an explosion occurred at a crude oil extraction facility killing the two employees who were carrying out welding work on top of a crude oil storage tank, which was connected to two adjacent tanks. The filling operation underway at one of the adjacent tanks caused inflammable vapours to move in the direction of the tank being welded via the breathing vent located beside the welders. The combustible cloud was ignited by welding sparks and then exploded. The investigation conducted by administrative authorities revealed that the workers (subcontractor’s employees) had failed to measure the explosive potential both before and during welding; moreover, no procedure had been adopted for hot work, nor were any jobsite controls in place for subcontractors. Lastly, the two subcontracted workers had not received any training in the risks associated with hot work.