
Nigeria is Africa's largest crude oil exporter but its production capacity has been slashed by thieves drilling into pipelines passing through winding creeks and waterways in the vast delta.
The underground industry is estimated to be worth hundreds of millions of dollars a year.
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A man carries a bucket of crude oil at an illegal refinery in the village of Isuini-biri in Nigeria's Bayelsa state May 15, 2012.
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A view of an illegal oil refinery is seen along the Awoba creek outside the oil hub city Port Harcourt in Nigeria's Delta region May 16, 2012.
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Smoke rises from an illegal crude oil refinery site in an Ogoni community in Nigeria's Niger Delta July 7, 2010.
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An oil slick flows at the base of a mangrove near an illegal oil refinery along the Diebu creek in Nigeria's Bayelsa state May 15, 2012.
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A man collects crude oil from a drum at an illegal refinery in the village of Isuini-biri in Nigeria's Bayelsa state May 15, 2012.
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A plastic container, which contains crude oil siphoned for an illegal refinery from a flow station, is seen on a canoe along the Diebu creek in Nigeria's Bayelsa state May 15, 2012.
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An aerial view during a media tour by oil company Royal Dutch Shell shows an illegal oil refining site with the runoff from crude oil covering the banks along the Imo river, west of Nigeria's oil hub city of Port Harcourt.
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A view of an illegal oil refinery is seen along the Ekulama creek outside the oil hub city Port Harcourt in Nigeria's Delta region.
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Smoke rises from an illegal oil refinery along the Diebu creek in Nigeria's Bayelsa state.
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A man paddles a canoe with plastic containers used to transport oil siphoned from pipelines through the Diebu creek in Nigeria's Bayelsa state May 15, 2012.
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Oil surfaces on water near an illegal oil refinery in Ogoniland outside Port Harcourt in Nigeria's Delta region.
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A signboard campaigning against oil pipeline vandalism is seen along a road in Yenagoa in Nigeria's Bayelsa state.
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A view of an illegal oil refinery is seen along the Awoba creek outside the oil hub city Port Harcourt in Nigeria's Delta region May 16, 2012.
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Labourers walk on a canoe used in siphoning crude oil for illegal refinery, after stealing the oil by tapping on a flow station, along the Diebu creek in Nigeria's Bayelsa state May 15, 2012.
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An aerial view during a media tour by oil company Royal Dutch Shell shows an illegal oil refining site with the runoff from crude oil covering the banks along the Imo river, 30 km (20 miles) west of Nigeria's oil hub city of Port Harcourt.
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An aerial view during a media tour by oil company Royal Dutch Shell shows locally built barges surrounded by the runoff from crude oil at an illegal oil refining site along the Imo river, 30 km (20 miles) west of Nigeria's oil hub city of Port Harcourt.
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A view of an illegal oil refinery is seen in Ogoniland outside Port Harcourt in Nigeria's Delta region March 24, 2011.
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A man's leg is coated in crude oil as he walks out of a polluted river in Bidere community in Ogoniland in Nigeria's delta region.
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Canoes used for siphoning crude oil to illegal oil refinery are scattered on a creek in Ogoniland outside Port Harcourt in Nigeria's Delta region.
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An aerial view during a media tour by oil company Royal Dutch Shell shows an illegal oil refining site with the runoff from crude oil covering the banks along the Imo river, west of Nigeria's oil hub city of Port Harcourt.
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A man samples crude oil at the bank of a polluted river in Bidere community in Ogoniland in Nigeria's delta region.
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A view of an illegal oil refinery is seen along the Ekulama creek outside the oil hub city Port Harcourt in Nigeria's Delta region.
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A view of an illegal oil refinery is seen in Ogoniland outside Port Harcourt in Nigeria's Delta region.
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Up to 500 people were burned alive when fuel from a vandalised pipeline exploded in Nigeria's largest city, Lagos, after thieves punctured the underground pipeline to siphon fuel into a road tanker.