WARRI, Nigeria (AP) — Local police are disputing claims that Nigerian oil militants struck another pipeline in the Niger Delta, saying an explosion was instead caused by a gas leakage.

Cordelia Nwawe, police spokesperson for Akwa Ibom state, said Friday that engineers were "working to rectify the leakage" from the pipeline owned by the Nigeria National Petroleum Corporation.

The Niger Delta Avengers claimed responsibility for the attack in a Twitter post on Thursday morning. Attacks in recent months have ended years of relative peace in the delta and cost Nigeria its place as Africa's biggest oil producer, now held by Angola.

Last week Nigeria's government ordered the military to halt attacks in the oil-producing south and urged militants to halt bombings to allow a dialogue, but the Niger Delta Avengers have refused negotiations.