Republican Sens. Chuck Grassley and Ron Johnson on Tuesday demanded answers on whether a top Justice Department official and Delaware state officials involved in the federal investigation into Hunter Biden's tax affairs have recused themselves due to potential conflicts of interest, and slammed the Justice Department for casting "a cloud" of "serious suspicion" over the probe. 

In a letter to U.S. Attorney for Delaware David Weiss, who is leading the investigation, Grassley, R-Iowa, and Johnson, R-Wis., questioned whether Nicholas McQuaid, who serves as the current principal deputy assistant attorney general for the Justice Department’s criminal division, "has or had any role in the Hunter Biden criminal case and whether he has been recused from it." 

DOJ HIRE IS FORMER COLLEAGUE OF HUNTER BIDEN DEFENSE ATTORNEY

Grassley and Johnson first raised questions about McQuaid to Attorney General Merrick Garland in February 2021, when McQuaid served as acting assistant attorney general for the Justice Department’s criminal division.

McQuaid, who spent the years prior to joining the Justice Department as a partner in the New York office of law firm Latham & Watkins, worked with Christopher Clark, who is currently representing Hunter Biden.

As principal deputy assistant attorney general for the criminal division, McQuaid has oversight of criminal investigations.

"This association creates a clear conflict of interest yet the Department has failed to provide adequate responses to answer the threshold questions about whether Mr. McQuaid has or had any role in the Hunter Biden criminal case and whether he has been recused from it," Grassley and Johnson wrote.

"In light of Mr. McQuaid’s clear conflicts in the Hunter Biden investigation, Attorney General Garland’s silence draws serious suspicion and has cast a cloud over the investigation – a cloud that could easily be removed if the Justice Department showed a modicum of transparency," they added.

Hunter Biden Joe Biden

Vice President-elect Joe Biden with his son Hunter on Capitol Hill on Jan. 6, 2009. (AP Photo/Charles Dharapak, File)

The senators went on to note that they "are unaware of any information that would call into question" Weiss’ "ability to lead this investigation."

GARLAND REFUSES TO ANSWER HUNTER BIDEN INVESTIGATION QUESTION, DOESN'T COMMIT TO APPOINTING SPECIAL COUNSEL

Last month, during Senate testimony, Garland was pressed on how Americans could have confidence that the Justice Department would conduct a "serious investigation" into the president’s son.

"Because we put the investigation in the hands of a Trump appointee from the previous administration, who is the United States attorney for the district of Delaware," Garland responded, referring to Weiss.

Garland Jan 6

Attorney General Merrick Garland speaks at the Department of Justice on Jan. 5, 2022, in Washington. (Carolyn Kaster-Pool/Getty Images)

"And because you have me as the attorney general who is committed to the independence of the Justice Department from any influence from the White House and criminal matters."

Despite the lack of concern with Weiss’ leadership, Grassley and Johnson took issue with the fact that "Delaware is the Bidens’ home state and Hunter Biden has acknowledged his connections with state officials in the past."

FEDERAL INVESTIGATION CONTINUES INTO HUNTER BIDEN EVEN AFTER HE PAID HIS TAX BILL

The senators referenced communications between Hunter Biden and his Chinese business partners in May 2018, in which he purportedly said he would "bring suit in the Chancery Court in Delaware – which as you know is my home state and I am privileged to have worked with and know every judge in the chancery court."

Sen Chuck Grassley

Sen. Chuck Grassley (Susan Walsh/Pool/AFP via Getty Images)

"This statement raises questions about the Bidens’ possible undue influence over judicial officers in the Delaware Court of Chancery and raises concerns that his asserted influence extends beyond the Court of Chancery," Grassley and Johnson wrote.

The senators went on to request information on which employees in the U.S. Attorney’s Office in Delaware have been recused from the investigation, and requested details on their identities and the timeline of their recusal.

The senators also demanded all communications between the U.S. Attorney's Office and McQuaid, as well as information on whether the Justice Department is providing "sufficient resources and support" to "properly execute the Hunter Biden criminal case."

HUNTER BIDEN UNDER FEDERAL INVESTIGATION FOR 'TAX AFFAIRS;' LINKS TO CHINA FUNDS EMERGE, SOURCES SAY

The senators also requested information on whether grand jury subpoenas have been issued to "Wells Fargo, USAA, Bank of America, TD Bank, JPMorgan Chase, PNC, Morgan Stanley, Citibank, Bank of New York Mellon, Bank of China and First National Bank of Omaha" for records related to Hunter Biden, his uncle, James Biden, Sara Biden, business partners John Walker, Eric Schwerin, Devon Archer and corporate entities "linked to them, including but not limited to, Hudson West III and the Lion Hall Group."

The senators also requested information on whether Weiss believes a special counsel should be appointed to take over the investigation.

The senators demanded answers by "no later than May 23, 2022."

Hunter Biden has been under federal investigation for his "tax affairs" since 2018, according to a source familiar with the matter. 

Sen. Ron Johnson

Sen. Ron Johnson (Bill Clark/CQ-Roll Call, Inc via Getty Images)

Fox News first reported in December 2020 that Biden was a subject/target of the grand jury investigation. A well-placed government source told Fox that a "target" means that there is a "high probability that person committed a crime," while a "subject" is someone you "don’t know for sure" has committed a crime."

The federal investigation into Hunter Biden was predicated, in part, by Suspicious Activity Reports (SARs) regarding foreign transactions.

Another source familiar with the investigation told Fox News in December 2020 that the SARs were regarding funds from "China and other foreign nations."

HUNTER BIDEN REQUESTED KEYS FOR NEW 'OFFICE MATES' JOE BIDEN, CHINESE 'EMISSARY' TO CEFC CHAIRMAN, EMAILS SHOW

A Treasury Department official, who did not comment on the investigation, spoke broadly about SARs, telling Fox News that SARs are filed by financial institutions "if there is something out of the ordinary about a particular transaction." 

The official told Fox News that the mere filing of a SAR does not mean there has been a criminal act, or violation of regulations, but instead flags that a transaction is "out of the ordinary" for the customer. The official noted, though, that an SAR could be part of a money laundering or tax investigation.

Meanwhile, the grand jury continues to investigate Hunter Biden’s international business dealings – even after he paid off a tax liability following the announcement of the probe into his "tax affairs."

CLICK HERE TO GET THE FOX NEWS APP

Hunter Biden, weeks after the 2020 presidential election, released a statement acknowledging the federal investigation of his "tax affairs."

"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," Biden said in the December 2020 statement.

Fox News' Ronn Blitzer contributed to this report.