President-elect Joe Biden’s son Hunter Biden is under investigation for his “tax affairs,” according to a statement sent by the presidential transition team. “I learned yesterday for the first time that the U.S. Attorney’s Office in Delaware advised my legal counsel, also yesterday, that they are investigating my tax affairs,” Hunter Biden said in the statement. “I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately.” David Weiss, Delaware’s district attorney, was appointed by Trump in 2018. His nomination was recommended by the state’s U.S. senators, Tom Carper and Chris Coons, both of whom are Democrats and allies of Biden.

According to CNN, the investigation began in 2018 and is centered on Hunter Biden’s business dealings in foreign countries, particularly China. One aspect under investigation, according to CNN, is a 2.8-carat diamond that Biden was reportedly gifted in 2017 by Chinese oil magnate Ye Jianming. Biden told The New Yorker in 2019 that he “knew it wasn’t a good idea to take it,” and gave the diamond to an associate.

“President-elect Biden is deeply proud of his son, who has fought through difficult challenges, including the vicious personal attacks of recent months, only to emerge stronger,” the statement from the transition team read. A source familiar with the matter wouldn’t disclose what the investigation was about but told The Daily Beast it was “not related to the attacks the Trump team and their allies made against Hunter during the campaign.”