U.S. intelligence agencies have found conclusive evidence that Russia provided hacked documents from the Democratic National Committee to WikiLeaks via a third party, Reuters reports. The news agency reportedly interviewed three U.S. officials with knowledge of the situation, who contend that intelligence agencies obtained the evidence of the Kremlin’s role in the wake of the November election–not before. Months earlier, authorities had concluded that Russia had directed the hacking, but it had not been clear if it had played a bigger role in the release of the leaked information. The report comes as top U.S. intelligence officials head to Capitol Hill on Thursday to testify before a special Senate hearing about the alleged hacking. Despite public statements released by both the CIA and the FBI, President-elect Donald Trump has voiced continued skepticism about the Kremlin’s role in the breach. Party leaders on both sides of the aisle have since called for a probe on the Russian role in the hack, and President Obama has taken heat from within the Democratic Party over failing to respond to the breach before the election. An intelligence report on the issue will be presented to Obama on Thursday and to Trump on Friday.