New whistleblower documents reveal that President Biden "was aware of Hunter Biden’s business arrangements and may have been involved in some of them," Republican Sen. Chuck Grassley said Monday, suggesting that the FBI has "voluminous evidence" related to the potential criminality of those ventures.

Grassley, R-Iowa, sent a letter Monday morning to Attorney General Merrick Garland, FBI Director Christopher Wray and U.S. Attorney for Delaware David Weiss detailing new whistleblower allegations that the bureau is in possession of "significant, impactful and voluminous evidence with respect to potential criminal conduct by Hunter Biden and James Biden." Weiss has oversight of the Hunter Biden investigation.

Grassley said the FBI has a series of documents in its possession related to information on Mykola Zlochevsky, the owner of Ukrainian natural gas firm Burisma Holdings. Hunter Biden sat on the board of that company.

"The documents in the FBI’s possession include specific details with respect to conversations by non-government individuals relevant to potential criminal conduct by Hunter Biden," Grassley wrote.

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"These documents also indicate that Joe Biden was aware of Hunter Biden’s business arrangements and may have been involved in some of them," Grassley said. He added it is "unclear whether the FBI followed normal investigative procedure to determine the truth and accuracy of the information or shut down investigative activity based on improper disinformation claims in advance of the 2020 election."

"It is also unclear whether U.S. Attorney Weiss has performed his own due diligence on these and related allegations," Grassley wrote.

Grassley and Sen. Ron Johnson, R-Wis., led an investigation into Hunter Biden beginning in 2019 and found that Obama administration officials "knew" that Hunter Biden’s position on the board of Burisma was "problematic" and that it interfered "in the efficient execution of policy with respect to Ukraine."

Tony Bobulinski, a former associate of Hunter Biden, talks with reporters before the presidential debate.

Tony Bobulinski, a former associate of Hunter Biden, talks with reporters before the presidential debate, Thursday, Oct. 22, 2020, in Nashville. (AP Photo/Evan Vucci)

Hunter Biden joined Burisma in April 2014 and reportedly connected the firm with consulting firm Blue Star Strategies to help the natural gas company fight corruption charges in Ukraine. During the time Hunter Biden was on the board of the company, Joe Biden was vice president and running U.S.-Ukraine relations and policy for the Obama administration.

Grassley also pointed to a summary of an FBI interview with Hunter Biden’s ex-business partner Tony Bobulinski from Oct. 23, 2020, in which Bobulinski stated that Hunter and James Biden created a business arrangement with foreign nationals connected to the Chinese government while Joe Biden was vice president.

Grassley said the summary of Bobulinski’s interviews states that work "remained intentionally uncompensated while Joe Biden was vice president."

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"After Joe Biden left the vice presidency, the summary makes clear that Hunter Biden and James Biden worked with CEFC and affiliated individuals to compensate them for that past work and benefits they procured for CEFC," Grassley wrote, referring to the now-bankrupt Chinese conglomerate CEFC China Energy.

Citing the summary, Grassley said that Hunter Biden, James Biden and their business associates created a joint venture that would serve as a "vehicle to accomplish that financial compensation."

The joint venture was known as SinoHawk Holdings, a partnership between the CEFC Chairman Ye Jianming and Hunter and James Biden. SinoHawk was 50% owned by Oneida Holdings LLC and 50% owned by Hudson West IV.

Hunter Biden Tony Bobulinsk FBI Grassley

Hunter Biden, son of U.S. President Joe Biden, arrives with wife Melissa Cohen Biden prior to President Biden awarding Presidential Medals of Freedom during a ceremony in the East Room at the White House in Washington, July 7, 2022.   (Kevin Lamarque)

Oneida was made of five evenly divided LLCs, according to the summary, one for each business associate, including Hunter Biden and James Biden.

Bobulinski told the FBI that 10% of Hunter Biden’s interest was "to be held for Joe Biden."

Fox News first reported in October 2020 about an email including a discussion of "renumeration packages" for six people in a business deal with CEFC. The email appeared to identify Biden as "Chair / Vice Chair depending on agreement with CEFC," in an apparent reference to CEFC.

The email included a note that "Hunter has some office expectations he will elaborate." A proposed equity split references "20" for "H" and "10 held by H for the big guy?" with no further details.

Bobulinski told Fox News at the time that "Hunter Biden called his dad ‘the Big Guy’ or ‘my Chairman,’ and frequently referenced asking him for his sign-off or advice on various potential deals that we were discussing."

Grassley's letter to Garland, Wray and Weiss included the Oneida Operating Agreement which included the "percentage of interest for each individual." The agreement was signed on May 22, 2017.

Grassley also said that the FBI "has a document within its possession that notes that then former Vice President Joe Biden met with Hunter Biden and his business associates at a conference in Los Angeles on May 2, 2017 and May 3, 2017."

Fox News first reported on those meetings in October 2020 after obtaining text messages between Bobulinski, Hunter Biden and James Biden. The messages seem to indicate that a meeting took place, though it is unclear what the substance of the meeting may have been.

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The conference was the Milken 2017 Global Conference, which, in part, was held at the Beverly Hilton Hotel, according to the program directory.

Joe Biden, on May 3, 2017, spoke at the conference and hosted "A Conversation with the 47th Vice President of the United States Joe Biden."

"Mrng plse let me knw if we will do early dinner w your Uncle & dad and where, also for document translation do you want it simple Chinese or traditional?" Bobulinski texted Hunter Biden on May 2, 2017.

"Not sure on dinner yet and whatever is the most common for a Chinese legal DOC," Hunter Biden replied.

"Chinese legal docs can be both, i’ll make it traditional," Bobulinski said.

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Hunter replied: "Dad not in now until 11- let’s me I and Jim meet at 10 at Beverly Hilton where he’s staying."

Bobulinski sent a text to James Biden, Joe Biden's brother, on the same day, May 2, 2017, saying: "Great to meet u and spend some time together, please thank Joe for his time, was great to talk thx Tony b."

The following day, May 3, 2017, Bobulinski sent another text to Jim Biden, saying: "Morning, please let me know all set for things this mrng. I don't have credentials to get into Milken so just want to make sure not an issue to get me in, where should we meet this mrng?"

The White House declined to comment on whether President Biden met with Bobulinski. 

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President Biden embraces his family first lady Dr. Jill Biden, son Hunter Biden and daughter Ashley after being sworn in during his inauguration on the West Front of the U.S. Capitol on Jan. 20, 2021 in Washington, D.C. During the inauguration ceremony, Biden becomes the 46th president of the United States. (Photo by Drew Angerer/Getty Images)

Grassley noted in his letter Monday that those meetings "have been publicly disclosed; however, the fact that the FBI maintains documents referencing these data points has not been made public before."

Grassley indicates that based on allegations provided to his office, Bobulinski's interview established a "sufficient basis to open a full field investigation on pay-to-play grounds" but says it is unclear if the FBI did so, or if the information is part of the ongoing criminal investigation by Weiss.

Grassley noted that the Justice Department and FBI "have not disputed the accuracy of the allegations" that he has made.

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"The Justice Department’s and FBI’s continued silence on these matters is deafening and further erodes their credibility," Grassley wrote. "Simply put, enough is enough – the Justice Department and FBI must come clean to Congress and the American people with respect to the steps they have taken, or failed to take, relating to the Hunter Biden investigation."

Grassley demanded information from the Justice Department on the Hunter Biden investigation by October 27, so Congress can "perform an independent and objective review."

President Biden has repeatedly denied speaking to Hunter about his business dealings. He has also denied, since the 2020 campaign trail, having any knowledge about or involvement in his son's business ventures.

Hunter Biden is currently under federal investigation for his "tax affairs."

Fox News first reported in July that the probe had reached a "critical stage," and that federal prosecutors were weighing whether to charge Hunter Biden with various tax and foreign lobbying violations, false statements and more.

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Fox News reported in July that the federal grand jury looking into Hunter Biden’s business dealings wrapped up its latest term in June and expired. A source, at the time, said no charges had been filed.

The FBI and DOJ confirmed receipt of Grassley’s letter but declined further comment. U.S. Attorney Weiss did not respond to Fox News' requests for comment.