KYIV, Ukraine (AP) — Ukraine’s Prosecutor General says that his office is reviewing all the cases that were closed by his predecessors, including several ones related to the owner of a gas company where former Vice President Joe Biden’s son sat on the board.

Ruslan Ryaboshapka told reporters Friday that prosecutors are auditing all the case that were closed or dismissed by the former prosecutors including several ones related to Mykola Zlochevsky, owner of the gas company Burisma that hired Hunter Biden in 2014.

A possible investigation into Burisma came to light last month when a whistleblower revealed that U.S. President Donald Trump in a phone call asked Ukrainian leader Volodymyr Zelenskiy to resume the probe into Joe Biden and his son. The July 25 call has since triggered an impeachment inquiry against Trump.