The temporary closure is expected to cut Nigeria's oil production by about 8 percent per day.
Aiteo Oil Exploration and Production Company said the shutdown took place Sunday.
The Nembe Creek Trunk Line has a carrying capacity of more than 150,000 barrels per day and is used to transport crude oil from the eastern Niger Delta to the Bonny Export Terminal in Rivers state in southern Nigeria.
The company said it suspected the fire may have occurred through "an illegitimate third-party breach."
Over the past two years, Nigeria has been steadily recovering in crude oil production, due to cessation of hostilities by the Niger Delta oil militants.
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