Nigeria's Trans Niger Pipeline, a major oil artery transporting crude from onshore oilfields to the Bonny export terminal, was shut after a blast that caused a fire, police said on Tuesday.

Nigerian oil consortium Renaissance Group, which now owns Shell's former onshore subsidiary that operates the pipeline, earlier confirmed the blast in coastal Rivers State and dispatched a team to investigate.

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The Trans Niger Pipeline (TNP), with a capacity of around 450,000 barrels per day, is one of two conduits that export Bonny Light crude from Nigeria, Africa's biggest oil producer.

Rivers State police said in a statement that the situation was now under control and that they had started investigations to determine the cause of the blast on Monday night.

"In connection with this, two individuals have been taken in for questioning as part of efforts to uncover any potential act of sabotage," the police said.

It was not immediately clear how long the TNP would be shut. A prolonged outage could, however, force its operators to declare force majeure on Bonny Light exports.

Pipeline sabotage and crude theft are some of the major reasons that oil majors like Shell, Exxon Mobil, Total, and Eni sold their onshore and shallow-water fields in Nigeria to concentrate on deep-water operations.

Renaissance Group, which includes Nigerian exploration and production companies Aradel Energy, First E & P, Waltersmith, and ND Western, along with the international energy group Petroline, completed the acquisition of Shell's former onshore assets last week.