The Republican-led House Oversight Committee has asked a Treasury Department official to testify in its investigation into the Biden family’s finances, according to a letter sent Friday obtained by NBC News.

It’s the most significant escalation in a long-running, and so far unsuccessful, effort by the GOP-led committee to gain access to alleged «suspicious activity reports» related to Hunter Biden and the Biden family that Republicans say are a part key to his investigation into the Biden family’s business practices.

Suspicious Activity Reports, or SARs, are required by federal law, and financial institutions must file them when they detect unusual transactions that could be signs of illegal activity.

The committee chair, Rep. James Comer, R-Ky., asked Isabella More, Treasury Department deputy assistant secretary for oversight, to testify at a March 10 hearing, suggesting the department has deliberately delayed filing documents. your committee in order to hinder your investigation.

“This hearing will examine the various justifications you have provided to the Committee regarding Treasury’s failure to submit requested documents, including SARs,” Comer wrote.

Eating in your letter suggests that «relevant SARs» to others have already occurred.

“The hearing will provide the Committee with invaluable information on Treasury’s approach to congressional oversight as the Committee considers legislation codifying what was once regular congressional access to SARs,” Comer wrote.

The Treasury Department did not immediately respond to a request for comment.

It is not clear if relevant SARs exist.

Republicans gained control of the House, and thus control of the oversight committee, during the November midterm elections. Comer that same month said investigations into Hunter Biden and other Biden family members and associates would be a priority.

Neither Biden has been charged with any crime.

Hunter Biden said in December 2020 that he was under federal investigation over his tax affairs.

Hunter Biden, 53, then said that «a professional and objective review of these matters will show that I handled my affairs legally and properly.»

President Joe Biden has rejected Republican plans to investigate his son.

“I think the American people will see all of that for what it is. It’s almost a comedy,» the president said on November 9. Press conference.

Last week, after a reporter yelled a question about whether the president’s ability to deal with China «is compromised by his family’s business relationships,» he said, «Give me a break man.» Other questions were also being shouted at that time.