Oil prices rose further on 5 August on continued fears about Iraqi output and renewed instability in Nigeria. Reports emerged on 4 August of at least 10 deaths in inter-tribal clashes in the oil-rich Niger Delta. Such clashes earlier in the year forced international oil companies in the country to shut-in production, and pushed prices up considerably. The new Iraq fears stem from a pipeline fire which broke out on 31 July near the Baiji refinery. Although the fire was extinguished two days later and the US Army Corps of Engineers (USACE) said that production was not affected, reports that the blaze was caused by sabotage highlighted the continued instability in the country and the consequent threat to a sustained resumption of exports at per-war levels. The dangers of operating in Iraq were also demonstrated on 5 August when an employee of Kellogg, Brown & Root, the Halliburton subsidiary appointed to carry out first phase reconstruction of the oil infrastructure, was killed when a bomb exploded under his vehicle.