Africa’s richest woman, Angola’s Isabel dos Santos, has been named as a formal suspect in a criminal investigation, the country’s attorney general is reported to have announced.

Dos Santos amassed a fortune estimated at $2.2bn (£1.7bn) while her father, José Eduardo dos Santos, was president of Angola. She is battling allegations of corruption and nepotism following the publication of Luanda Leaks, an investigation by the Guardian and other media led by the International Consortium of Investigative Journalists. She denies all wrongdoing.

Q&A What is the Luanda Leaks investigation? Show The Luanda Leaks project is based on a trove of 715,000 emails, charts, contracts, audits and accounts detailing the business operations of Isabel dos Santos, the daughter of the former president of Angola. The files were initially obtained by the anti-corruption charity Platform to Protect Whistleblowers in Africa (PPLAAF), which shared them with the International Consortium of Investigative Journalists (ICIJ). The documents, which cover a period between 1980 and 2018, have been reviewed by more than 120 journalists from 37 media outlets, including the Guardian, the BBC and the Portuguese newspaper Expresso.

The allegations against Dos Santos relate to suspected maladministration and misappropriation of funds during her 18-month term as chair of the nation’s state oil company, Sonangol, according to reports of a press conference given by the attorney general, Heldér Pitta Grós, in Luanda.

“Isabel dos Santos is accused of mismanagement and embezzlement of funds during her tenure at Sonangol,” he told a news conference Wednesday evening.

The Angolan authorities will now conduct a criminal investigation to determine whether she should be charged with these crimes.

Angola is the second-largest oil-producing nation in Africa after Nigeria, and its state oil company is central to the economy, accounting for some 90% of exports.

Alongside Dos Santos, Pitta Grós named a number of her associates as suspects. According to the Portuguese news agency Lusa, they are: Sarju Raikundalia, the former chief financial officer of Sonangol; Mário Leite da Silva, the chairman of the board of directors of Banco de Fomento Angola (BFA); Paula Oliveira, a friend of Isabel dos Santos; A director of Eurobic, a bank in which the former president’s daughter is the largest shareholder, was the fourth suspect named.

All of those named are currently outside Angola, the attorney general said, and will be notified of their status as defendants.

“At the moment, the concern is to notify and have them come to justice voluntarily,” Pitta Grós is reported to have told the press conference, adding that if this goal was not achieved, his office would resort to other legal instruments, including issuing international arrest warrants.

Dos Santos responded to an email about the allegations, but made no comment on them.

Raikundalia issued his first comments about the case in response to the announcement.

“In the evening of 22nd January, I read some press releases, stating that I’m a suspect in a criminal inquiry by Angolan government prosecutors. I would like to draw your attention that I have not been formally notified of such action,” he said in an email to the Guardian.

He said he had previously written to the attorney general to express his willingness to provide any information required by Angolan prosecutors.

By the time of publication, Dos Santos, Oliveira and Leite da Silva had not responded to requests for comment.

A spokeswoman for Portugal’s public prosecutor’s office told Reuters that Pitta Grós and Portugal’s attorney general, Lucilia Gago, would meet in Lisbon Thursday. It is not known what they plan to discuss.

The Luanda Leaks exposed numerous schemes apparently used by Dos Santos and her husband to obtain Angolan state funds during her father’s presidency.

The privately owned Portuguese bank Eurobic has announced that Dos Santos will be quitting as its largest shareholder after earlier saying it had barred her and her family as customers.

In a statement on Wednesday, the Lisbon bank said Dos Santos had decided to exit its share register. She holds 42.5% of the stock. The bank said the sale process was already under way, and she was expected to find a buyer “in a very short period” due to the existence of interested parties.

In a statement responding to the Luanda Leaks, Dos Santos and her husband said they owed their success to hard work and business acumen. She has accused Angola’s current president of pursuing a “politically motivated witch-hunt” against her and her family.