US oil giant ExxonMobil’s Nigerian subsidiary said on Friday it may not meet contractual obligations on exports from Nigeria owing to pipeline repairs.

“Mobil Producing Nigeria … has declared a force majeure due to the difficulty in meeting projected liftings because of repair work on a section of the joint venture’s pipeline,” the company said in a statement.

Force majeure is a legal term releasing a company from contractual obligations due to circumstances beyond its control.

“We are working to minimise downtime and have notified appropriate regulatory agencies and purchasers,” ExxonMobil said.

A company spokesman in Lagos declined to disclose the volume of crude affected or to provide the location of the pipeline. He also declined to say what caused the damage.

The firm’s Qua Iboe export terminal in southern Nigeria remained open.

“MPN continues to produce oil from the facilities that are not covered by force majeure,” it said.

Pipeline damage and associated spills are common in the Niger Delta region as a result of oil theft to feed the lucrative black market.

Militants claiming to be fighting for a fairer distribution of oil revenue have also blown up pipelines, though such attacks have decreased sharply since a 2009 amnesty deal.

ExxonMobil is a major operator in Nigeria, Africa’s biggest oil producer and its most populous nation. Nigeria produces some two million barrels of crude per day.