The United States Senate is weighing an investigation into Joe Biden’s dealings with Ukraine as vice president after his son’s business ties to the Eastern European country have come under scrutiny.

Sen. Ron Johnson (R-WI), the chairman of the Senate Homeland Security Committee, is reportedly considering an investigation into the former Vice President, according to sources that spoke to the Washington Post. The senator, himself, appeared to confirm an investigation was likely when speaking to reporters about the topic on Wednesday.

“We have and will continue to gather information and conduct oversight on alleged misconduct within government agencies,” Johnson said.

The move comes after President Donald Trump suggested the Ukrainian government investigate Hunter Biden’s tenure on the board of directors of Burisma Holdings. The younger Biden joined the company in 2014, purportedly making as much as $83,000 per month, to consult on legal services. The appointment immediately raised questions from ethics watchdogs in both the U.S. and Europe about the true nature of his role, since he possessed no background in either the energy industry or Ukraine.

Around the same tim Hunter Biden joined Burisma, his father was appointed as the Obama administration’s point man on Ukraine. Even more troubling is that at the time of the appointment, Burisma was attempting to sway western leaders after its founder, Mykola Zlochevsky, was accused of money laundering and had his assets seized in Great Britain. Zlochevsky is rumored to be one of eastern Europe’s leading oligarchs and has strong political ties to former Ukrainian President Viktor Yanukovych — a staunch ally of Russian President Vladimir Putin.

Even more troubling is the fact that in 2016, Joe Biden pressured the Ukrainian government to fire its top prosecutor, Victor Shokin, who was known to be investigating Zlochevsky and Burisma. Officially, the former vice president has claimed his threat to withhold U.S. aid if Shokin was not removed came from the Obama administration, which had lost confidence in the prosecutor’s abilities to root out corruption.

The explanation, however, was only muddied when Shokin’s successor, who had previously served a prison sentence for public corruption, closed the investigation into Burisma and Zlochevsky.

The appearance of impropriety on the part of the Bidens has also been underscored by the inability of father and son to get their stories straight. Last week the former vice president claimed to never have discussed his son’s business ties with Ukraine during a campaign appearance in Iowa.

“I have never spoken to my son about his overseas business dealings,” Joe Biden angrily said, before pivoting the conversation to Trump’s alleged misuse of power.

The former vice president’s claim, though, directly contradicts his son’s on the topic. The younger Biden admitted during a series of candid interviews for a New Yorker profile published in June that he in fact had discussed his foreign business interests with his father on at least one occasion.

“Dad said, ‘I hope you know what you are doing,’ and I said, ‘I do,’” Hunter Biden told the magazine.

If Johnson were to open a probe into the former vice president, it would likely overlap with an existing probe by Sen. Chuck Grassley (R-IA) into Hunter Biden’s business ties to China. In August, Grassley, the chairman of the Senate Finance Committee, began investigating the Obama-Biden administration’s decision to approve the sale of a U.S. company with insight into “military applications” to the Chinese government and an investment firm run by Hunter Biden.

In particular, Grassley has questioned if the decision to approve the sale violated the White House’s ethical guidelines governing conflicts of interest.