Angola’s Supreme Court has asked President José Eduardo dos Santos to respond to an inquiry on why he appointed his daughter as head of the state oil firm, according to court documents seen by Reuters.

Dos Santos appointed his daughter Isabel as chief executive of state oil firm Sonangol in June. Angola, a member of OPEC, is currently Africa’s largest oil producer because of militant attacks and other problems that have cut output in Nigeria.

The court was acting in response to a case filed by 14 Angolan lawyers who accused the president of nepotism and violation of the Angolan probity law. The presidency was not immediately available to comment.