The Human Rights Group, Amnesty International has accused major oil companies of covering up the true cause of oil spills in Nigeria to avoid compensation claims. One of the companies, Shell has disputed the accusation saying it working hard to ensure greater transparency. There are hundreds of oil spills in Niger delta every year. The oil companies say the vast majority are caused by sabotage and theft from the pipelines. But Amnesty International says in order to get out of paying compensation these oil companies including Shell sometimes cite sabotage when in fact it is poor maintenance.