House Republicans plan to hold a contempt of Congress hearing against FBI Director Christopher Wray on Thursday, escalating a probe into President Joe Biden’s actions as vice president.

The dramatic move comes after Wray’s refusal to comply with a subpoena for unclassified FBI-held document or documents that, Republicans say, link Biden to a $5 million “bribery scheme” involving an unnamed foreign national.

Spokespeople at the FBI and Justice Department did not respond to requests for comment.

If a majority of the Oversight Committee vote to hold Wray in contempt, the measure would be sent to the full House for a floor vote and a likely referral to the Justice Department.

Justice officials are unlikely to prosecute Wray, but a protracted civil court battle between two branches of government could ensue.

Representative James Comer, the committee’s chair, announced the Thursday hearing after, he said, the FBI refused in a briefing Monday to hand over a “confidential” source document.

“The confidential human source who provided information about then-vice president Biden being involved in a criminal bribery scheme is a trusted highly credible informant who has been used by the FBI for over 10 years and has been paid over six figures,” Comer said.

Both Comer and Jamie Raskin, the committee’s top Democrat, were able to confirm in the FBI briefings Monday the document does exist.

But Raskin called the document “second-hand hearsay.” The FBI’s informant, Raskin said, wasn’t directly involved.

“So, it’s not the source’s information,” Raskin said. “It’s information that he reported from a conversation from someone else that he was not able to verify or authenticate.”