Officials say Nigeria is suing several major oil companies for $12.7 billion of oil allegedly exported illegally to the United States between 2011 and 2014.

The Federal High Court in Lagos begins hearings next week in cases filed against Nigerian subsidiaries of U.S. multinational Chevron, British-Dutch Shell, Italian ENI's Agip, France's Total and Brasoil of Brazilian Petrobas.

Officials familiar with the cases say the government alleges that the companies did not declare more than 57 million barrels of crude oil shipments. That was deduced from audits of declared exports and what was unloaded in the United States.

The officials spoke on condition of anonymity because the cases still are in court.

Oil companies did not immediately respond to requests for comment.