Shell, in a statement to Bloomberg News, said production resumed at the Bonga field in Nigeria. The field was producing around 200,000 barrels of oil per day before the company shut it down following a December leak.
Shell closed operations at the offshore Bonga production platform following the discovery of a leak from an export line feeding a tanker. The company said preliminary estimates indicate less than 40,000 barrels of oil spilled. Bloomberg noted, however, that estimate made it one of the worst in Nigeria in decades.
Shell said it was investigating what it said was a "faulty line" from the offshore production platform. Shell has a legacy of oil spills in the Niger Delta region. The company blames saboteurs and oil bandits for most of the accidents.
Meanwhile, force majeure was declared on a field tied to an export terminal in Nigeria because of leaks elsewhere, the company said.
Nigeria is faced with security challenges because of a decision by the government to end a fuel subsidy in place for 38 years. Tensions are further escalated by threats from Islamic militants Boko Haram.