The daughter of a former president of Angola failed to respond to her first summons from state prosecutors to answer questions about her time running Sonangol, the state oil company, Angola's state news agency Angop reported.
Isabel dos Santos is allowed to provide reasons for not appearing three times, Angop said late Monday, citing a source in the prosecutor general's office. After that, she might face arrest.
The investigation relates to allegations made in February by current Sonangol Chairman Carlos Saturnino. He said an internal audit had uncovered suspicious transactions overseen by dos Santos, including a payment of $38 million made to a Dubai-based company she approved after she was dismissed from Sonangol.
Dos Santos has denied wrongdoing and accused Saturnino of trying "to rewrite history." A spokeswoman for dos Santos said she had not received any summons.
"Ms. Isabel dos Santos was surprised when she was informed by the media that she had been notified to respond regarding her management at Sonangol," the spokeswoman said.
Angop said the summons was issued July 17 for her to appear before prosecutors the next day.
A spokesman for the prosecutor general's office did not immediately respond to a request for comment.
President Joao Lourenço, who took office in September when Jose Eduardo dos Santos stepped down after nearly four decades in power, has acted to sideline powerful figures associated with his predecessor and tackle rampant corruption.
He sacked Isabel dos Santos as chair of Sonangol and her half brother Jose Filomeno dos Santos as head of the Sovereign Wealth Fund. The latter is also a suspect in a fraud case involving a transfer of $500 million from the central bank. He has said he is cooperating with authorities.
State prosecutors opened an investigation into the allegations by Saturnino against Isabel dos Santos in March but have issued no public statements since.