KYIV, Ukraine — Ukraine is reviewing past investigations into the owner of a company that once employed former Vice President Joe Biden's son as a board member, the country's chief prosecutor said Friday.

The move is part of a wider audit into previous cases concerning wealthy businessmen in Ukraine, the prosecutor's office said in a statement.

It said one of the businessmen named in around 15 of these cases is Mykola Zlochevskyi, the owner of the Burisma energy company that paid Hunter Biden to sit on its board.

Burisma is a crucial component of the impeachment inquiry into President Donald Trump. The president is accused of pressuring Ukraine's government to dig up dirt on the Bidens in exchange for military aid and other incentives.

There is no evidence of wrongdoing by either Joe or Hunter Biden.

Download the NBC News app for full coverage of the impeachment inquiry

Ruslan Riaboshapka, Ukraine's general prosecutor, told a press conference Friday that he aimed to review cases that "have been closed in violation of the law or other procedural violations" — potentially leaving the door open for them to be revived.

Speaking later to NBC News, Riaboshapka said the decision to review high-profile closed cases came after he took office in August, meaning it was taken after a July 25 phone call between Trump and Ukrainian President Volodymyr Zelenskiy.

According to a White House memo of the call, the U.S. president asked his counterpart to investigate the Bidens.

"As soon as I entered office, we began to do some auditing of the proceedings, so that by Nov. 20 we would finish everything and pass [it] on to the appropriate jurisdiction," the prosecutor said.

"And in those cases where there were illegal decisions [to close cases] to further review them. We have already reviewed, and made determinations on, dozens of such cases."

Asked whether the decision was influenced in any way by Zelenskiy or his office, Riaboshapka said: "In no way is the President's Office involved in any matter with the GPU [Prosecutor General's Office]. Their office does not interfere with our work."

Texts released late Thursday showed how two U.S. ambassadors pushed Ukraine to publicly announce they were investigating Trump's political opponents, explicitly linking this request to whether Zelenskiy would be granted a visit to the White House.

Despite evidence to the contrary, Trump claims that the elder Biden pressured Ukraine to fire its former prosecutor because he was investigating the firm paying his son.

In fact, the then vice president was among many international figures — including the European Union and International Monetary Fund — calling for the prosecutor's removal. This was because he was widely seen as too weak on fighting Ukraine's endemic corruption problems.

Riaboshapka was appointed in August by Zelenskiy, who has made tackling corruption one of his central policy aims.

Alexander Smith reported from London, Marc Smith and Gabe Joselow reported from Kyiv.

CORRECTION (Oct. 4, 2019, 11:21 a.m. ET): An earlier version of this article misstated where the interview with Ruslan Riaboshapka took place. It was over the phone, not at his office.