Abuja - ExxonMobil's Nigeria unit said on Tuesday it was helping clean up an oil spill near its facility off the southeast coast, although the company wasn't yet sure what caused the leak.
Mobil Producing Nigeria, a joint venture between ExxonMobil and the state oil firm, confirmed last week oil had been sighted near Ibeno in Akwa Ibom state but the source was unknown.
Local fishing communities blame Mobil for the spill, which they say has cut off their livelihood.
"Mobil... confirms it is assisting with the clean-up in cooperation with local authorities," company spokesman Nigel Cookey-Gam said.
"The source of the hydrocarbon remains unknown as fingerprinting of collected samples is ongoing ... Mobil remains committed to ensuring that the health and environment of our neighbouring communities are protected."
Oil spills are common in Africa's top energy producer and stretches of the Niger Delta, a fragile wetlands environment, are coated in crude. Thousands of barrels are spilled every year and lax enforcement means there are few penalties.
Oil firms say the majority of spills are due to armed oil thieves hacking into or blowing up pipelines to steal crude, an activity they estimate saps nearly a fifth of Nigeria's output.