The FBI is investigating whether the exposure of Hunter Biden’s emails was linked to a foreign intelligence effort to undermine the US election.
Agents seized a laptop and hard drive containing the emails at the end of last year, according to a subpoena issued by a US district court in Delaware. They are looking at potential foreign involvement, NBC News reported.
On Wednesday the New York Post published some of the emails, including one from an adviser to Ukrainian energy company Burisma, for which Hunter Biden worked while his father was vice president.
In the 2015 email, the authenticity of which has not been verified, the adviser thanked Hunter Biden for setting up a meeting with his father. Joe Biden’s campaign has denied any such meeting took place.
It has previously been reported that Burisma’s computers were infiltrated by Russian military hackers towards the end of last year.
Shortly before the 2016 election Russian hackers breached the Democratic National Committee’s systems, leading to the leaking of emails embarrassing to Hillary Clinton.
According to the New York Times US intelligence began suspecting last month that emails taken from Burisma could emerge publicly before the 2020 election.
The owner of a computer repair shop in Delaware has come forward publicly to say he made a copy of the hard drive, before it was seized by the FBI, and passed it to an associate of Rudy Giuliani, Donald Trump’s personal lawyer. Mr Giuliani then passed it to the New York Post.
It is not yet clear whether Hunter Biden, or someone else, dropped the laptop off at the repair shop and abandoned it there. Facebook and Twitter both took steps to limit distribution of the New York Post story by their users, leading to accusations of censorship by Republicans.
Twitter later changed its policy on material it suspected of being hacked, saying it would label content to that effect rather than blocking users from sharing it.
Meanwhile, Mr Trump and Mr Biden took part in competing town hall events, broadcast on separate television networks at the same time.
Preliminary viewing figures suggested Mr Biden won the competition for viewers with 12.7 million to Mr Trump’s 10.4 million.
In his town hall Mr Trump refused to denounce the QAnon conspiracy theory, which falsely claims the US government is controlled by a “deep state” cabal of anti-Trump satanist paedophiles.
The president said: “I know nothing about QAnon. I know very little. What I do hear about it, they are very strongly against paedophilia. I do agree with that.”
He was also questioned over his decision to retweet a false conspiracy theory, from a QAnon-linked Twitter account, that Navy Seals killed a body double of Osama bin Laden, and that the Obama administration covered it up.
Mr Trump said he was just “putting it out there” and “people can decide for themselves”. Savannah Guthrie, host of the town hall, responded: “I don’t get that. You’re the president, not someone’s crazy uncle.”
Attacking the president for his handling of the pandemic, Mr Biden said: “We’re in a situation where we have 210,000 plus people dead and what’s he doing? Nothing. He’s still not wearing masks.”
Later, Mr Trump shared on Twitter a post from a satirical website. The false report said that Twitter had “shut down its entire social network” on Thursday to prevent the spread of negative news about Mr Biden. Mr Trump wrote: “Wow, this has never been done in history.”
the Republican National Committee filed a complaint with the Federal Election Commission over Twitter’s decision to limit sharing of the New York Post story.
The committee argued it was an “illegal corporate in-kind political contribution” to Mr Biden’s campaign.
It accused Twitter of being a “partisan actor” which had “used its corporate resources to provide active support for Joe Biden’s campaign in violation of federal law.”
Last year, the White House was warned by US intelligence officials that Mr Giuliani was the target of a Russian influence operation, the Washington Post reported.
Robert O’Brien, Mr Trump’s national security adviser, reportedly told the president Mr Giuliani could unwittingly be passing on Russian misinformation, the newspaper said.
Mr Trump reportedly “shrugged his shoulders” and said “That’s Rudy.”
A National Security Council spokesman said: “The characterisation of the meeting as described in reports is not accurate.”