Block 5A is an oil concession in South Sudan. After oil field development began during the Second Sudanese Civil War, Block 5A was the scene of extensive fighting as rival militias struggled for control. Out of an original population of 240,000, an estimated 12,000 were killed or died of starvation and 160,000 were displaced by force. Production started in 2006. There is evidence that the environmentally sensitive marshlands beside the Nile are becoming polluted.