A probe by Senate into whether state oil firm NNPC improperly withdrew money has expanded with the amount under investigation doubling to over $2.2 billion, a committee said on Wednesday.

Senate last week voted to probe withdrawals of $1.05 billion by Nigerian National Petroleum Corporation (NNPC), from NLNG, a venture owned by the state oil firm and foreign energy companies, without approval.

The committee led by Mr Bassey Akpan, chairman of Senate committee on gas, said on Wednesday it had found more withdrawals in excess of what it set out to investigate.

Akpan asked NNPC and central bank officials to provide documents to back up the withdrawals, carried out at various periods between 2016 to 2018.

NNPC officials said documents were being assembled ahead of next hearing due on Nov 22 and declined to comment further.

Premium Times newspaper reported last week that NNPC had used the portion of NLNG earnings that should have been passed to local and federal state authorities to fund the state oil firm’s fuel purchases and subsidies during a shortage in late 2017 and early 2018.

The shortages left people queuing for hours at filling stations and saw NNPC spend at least $5.8 billion on fuel imports.

NLNG, which produces liquefied natural gas (LNG) for export, is a joint venture company owned by NNPC and foreign energy firms Royal Dutch Shell Plc, Total SA and ENI.

Reuters