During Tuesday remarks on the Senate floor, Iowa Republican Sen. Chuck Grassley questioned the FBI’s motivations for redacting portions of an unclassified document detailing an alleged bribery scheme involving then-Vice President Joe Biden when the bureau permitted House lawmakers to view it. He further vowed to investigate the bureau’s efforts to corroborate the allegations upon receiving them.

Grassley released the full document in its unredacted form last week. The form FD-1023 detailed allegations that Burisma CEO Mykola Zlochevsky hired Hunter Biden to the company’s board to secure his father’s aid in quashing a probe from then-Ukrainian Prosecutor General Viktor Shokin. Hunter and another Biden ostensibly received $5 million each for their efforts. President Biden has publicly taken credit for getting Shokin fired. The document also points to the alleged existences of audio recordings including Joe Biden to substantiate the exchange.

References to those tapes were redacted when the House was permitted to view the form, a decision with which Grassley took issue.

“The FBI provided a highly redacted version to the House Committee on Oversight, and in the process ignored the Senate access to that document,” he said Tuesday. “That version redacted references to the alleged audio recordings between then-Vice President Biden, Hunter Biden, and the foreign national.”

“It also redacted references to text messages and financial records that allegedly existed to prove the criminal act was done. Those redactions are an obstructive conduct by the United States. Why? Because this was an unclassified document. It’s not even marked law enforcement sensitive,” he continued.

Grassley went on to highlight extensive media reporting calling the allegations unverified, saying “[b]ut the Justice Department and the FBI have not told us what they did to investigate the 1023 documents. So then, since the FBI hasn’t told us anything about their investigation of 1023, if they did any. So how does the media then know that it is unverified?”