Nigeria, Africa’s largest oil producer, is losing billions of dollars a year due to corruption and inefficiency reported Forbes.

The country has come under scrutiny as its president, Muhammadu Buhari has worked to reduce corruption as promised during his campaign. In June Buhari dissolved the board of the Nigerian National Petroleum Corporation (NNPC), stated Bloomberg.

A new report by a US-based governance group alleges that the NNPC “suffers from high corruption risks and fails to maximize returns for the nation.”

Between half and a quarter of daily production is funneled by the NNPC to the country’s four domestic refineries. Payment for roughly half that amount goes missing from government coffers every day, as money is siphoned off at each step.

This graft has come to light as the Nigerian government—which obtains 70% of its revenues from oil resources—grapples with a low price environment.