A Republican U.S. lawmaker heading a congressional probe into Hunter Biden’s business dealings asked the National Archives on Thursday for emails between President Joe Biden and his 53-year-old son.

House of Representatives Oversight Committee Chairman James Comer called on the official depository of U.S. records to produce unredacted emails and other documents from 2015 and 2016, when the elder Biden was vice president and his son sat on the board of the Ukrainian energy company Burisma.

House Republicans are mulling a possible impeachment inquiry against the elder Biden, based partly on allegations that the president, his son and other family members have engaged in financial misconduct, allegations the White House strongly denies. They have not produced evidence of financial misconduct by the president.

The White House had no immediate comment.

David Weiss, the newly elevated U.S. special counsel leading the Justice Department’s investigation of Hunter Biden, last week said he may be heading to trial on charges of tax evasion and a gun charge, after a judge refused to accept a proposed plea deal to settle the charges

That raises the possibility that President Biden’s son could face a criminal trial as his father is seeking reelection, in a likely rematch with former President Donald Trump, who faces his own broad array of legal woes.

Late last month, a former Hunter Biden business associate told investigators that the president’s son gave the impression to Burisma executives that he had leverage because of his father and sold those family ties as part of his business brand.

But the witness, Devon Archer, said that while Hunter Biden had his father talk to associates and others by speakerphone about 20 times over 10 years, the conversations did not involve any business dealings. Archer said he was not aware of any wrongdoing by the elder Biden.

“Joe Biden has stated there was ‘an absolute wall’ between his family’s foreign business schemes and his duties as vice president. But evidence reveals that access was wide open for his family’s influence peddling,” Comer alleged in a statement.

“The National Archives must provide these unredacted records to further our investigation into the Biden family’s corruption,” the Republican said.

After the proposed plea deal collapsed, Hunter Biden pleaded not guilty in July to charges of failing to pay taxes on more than $1.5 million in income in 2017 and 2018 despite owing more than $100,000. He did not enter a plea in a separate case where he is charged with unlawfully owning a firearm while using illegal drugs, which is a felony.