Workers, seen through a pipe, look on at the scene of an oil pipeline fire in Dadabili, Niger state April 2, 2011. Nigeria postponed parliamentary elections nationwide until Monday after voting materials failed to arrive in many areas, a major blow to hopes of a break with a history of chaotic polls in Africa's most populous nation. Voting materials also failed to arrive in large parts of the southern oil-producing Niger Delta. REUTERS/Afolabi Sotunde (NIGERIA - Tags: ENVIRONMENT ENERGY POLITICS ELECTIONS)