In a blow to House Republicans’ impeachment inquiry into the president, the CIA refuted a whistleblower’s allegations that the agency sought to block a federal investigation into President Joe Biden’s son, Hunter Biden, on Thursday.

House Oversight Committee Chair James Comer, R-Ky., and House Judiciary Committee Chair Jim Jordan, R-Ohio, sent a letter to the CIA in March saying a whistleblower informed them the CIA blocked the Department of Justice and IRS investigators from interviewing a benefactor of Hunter Biden.

The CIA called the allegation “false” in a letter obtained by USA TODAY and sent to the chairs on Thursday.