Hunter Biden, the son of President-elect Joe Biden, said Wednesday that the U.S. attorney’s office in Delaware is investigating his tax affairs.

“I take this matter very seriously but I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisors,” Hunter Biden said in a statement issued by the Biden-Harris transition team.

He said that he learned of the investigation on Tuesday when his lawyer was advised of the investigation by federal prosecutors.

The transition team also issued a statement describing the president-elect as “deeply proud of his son, who has fought through difficult challenges, including the vicious personal attacks of recent months, only to emerge stronger.”

The transition team did not offer any more information about the investigation. CNN reported that federal authorities are investigating Hunter Biden’s business dealings with foreign countries such as China, including potential violations of tax and money laundering laws. The investigation reportedly began as early as 2018.

The revelation comes days before Joe Biden’s election as president will become official with the meeting of the Electoral College. It is certain to open up the Biden family to further scrutiny from President Trump and his allies. Trump has refused to concede the election.

Hunter Biden withstood a mountain of attacks from Trump during the primary and general election campaigns as a result of his foreign business dealings. He served on the board of a Ukrainian energy company when Joe Biden served as vice president under the Obama administration.

Hunter Biden said in an ABC News interview last year that he used “poor judgment” when he decided to take the role because it opened up his father to attacks from his opponents but said he did nothing improper.

Trump was impeached by the House of Representatives last year for pressing Ukraine’s president to investigate the Bidens’ affairs.

Hunter Biden is the president-elect’s only living son. His other son, Beau Biden, died in 2015 after a battle with brain cancer.

A spokesperson for the U.S. attorney’s office in Delaware declined to comment, citing the Justice Department’s policy not to comment on ongoing investigations.

The Hill