LAGOS — Shell said Sunday it had shut down a key pipeline damaged by fire after what was suspected to be an attempt to steal crude, a move that would affect some 150,000 barrels of oil per day.

Shell's Nigeria branch had "shut the 28-inch Bomu-Bonny Trunkline after discovering a fire on it early this morning (Sunday)," a statement said.

"A burning vessel, thought to be involved in the theft of crude oil from the line, was sighted near the incident site ... Some 150,000 barrels of oil per day is deferred."

The incident occurred near the Okololunch community in the eastern Niger Delta, the oil-producing region in southern Nigeria. The line conveys crude to the Bonny export terminal.

Shell, the biggest producer in Nigeria, said it was mobilising to fight the fire, investigate and repair the line.

Nigeria is Africa's largest oil producer. Oil theft for sale on the black market has been a major problem.

Shell has said there have been estimates that 150,000 barrels of oil and condensate are stolen in the country each day. Nigeria currently exports more than two million barrels per day.