Accounting firm PricewaterhouseCoopers (PwC) has started work with the federal auditor-general to carry out an audit on the Nigerian National Petroleum Corporation (NNPC) over an alleged missing $20bn in oil revenues. Speaking at the World Economic Forum on Africa in Abuja on 8 May, finance minister Ngozi Okonjo-Iweala said the work, which began the previous week, should be completed within 16 weeks. “Our feeling is that the only way is to have a forensic audit that would let Nigerians know the truth about the issue,” she said.