Federal prosecutors in Delaware are investigating President-elect Joe Biden’s son Hunter Biden over tax issues, the transition team announced Wednesday.

News of the investigation comes just as Joe Biden is set to announce his nominee for attorney general of the United States. Hunter Biden had been a constant target for President Donald Trump during the 2020 campaign.

Hunter Biden said in a statement that the US Attorney’s Office in Delaware informed his legal counsel about the investigation on Tuesday. The US Attorney’s Office declined to comment, citing Justice Department policy. 

“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.

Joe 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,” a statement from the transition team said. 

A CNN reporter was working on a story about the investigation and had been in contact with Hunter Biden’s legal counsel when the transition team for Joe Biden and Vice President-elect Kamala Harris sent out its press release. The reporter, senior justice correspondent Evan Perez, reported that the investigation began in 2018, but was put on hold ahead of the 2020 election under DOJ policy.

Investigators in the probe have been looking at whether Hunter Biden and his associates violated tax and money laundering laws in business dealings in foreign countries ― specifically China, as first reported by CNN and confirmed by The Associated Press. Some of those transactions reportedly involved people the FBI believe resulted in counterintelligence concerns, which CNN said is common when dealing with Chinese businesses.

Weeks before the election, Trump supporters used the existence of a laptop they said was tied to Hunter Biden — as well as the surfacing of someone who alleges he had business dealings with him — to question Joe Biden’s knowledge of his son’s activities in countries like Ukraine and China. The president-elect maintains that he did not speak with Hunter Biden about his business dealings, and has denied ever taking money from a foreign country.

The laptop became public in October when The New York Post reported on emails it alleged had come from Hunter Biden’s laptop, and that the publication said it received from Trump’s personal lawyer Rudy Giuliani.

The tax probe on Hunter Biden has nothing to do with the laptop, according to the AP, who cited an anonymous source familiar with but not authorised to discuss the matter. 

Joe Biden addressed his son’s business dealings in an interview last week with CNN’s Jake Tapper, pledging to maintain an independent Justice Department free of any perceived conflicts of interest.

“My son, my family will not be involved in any business, any enterprise that is in conflict with or appears to be in conflict, where there’s appropriate distance from the presidency and government,” the president-elect said.