The FBI is investigating the alleged hack of former President Donald Trump’s campaign, the agency said Monday, days after the campaign blamed Iran for a breach.

“We can confirm the FBI is investigating this matter,” the agency said in a short statement.

After several reporters received copies of an internal vetting document on vice presidential nominee Sen. JD Vance (R-OH), the Trump campaign said “foreign sources hostile to the United States” were responsible for the compromise. They blamed Iranian hackers — citing a report released by Microsoft last week that detailed how operatives linked to Tehran targeted an unnamed presidential campaign, among other covert efforts to influence the race.

Last month, the Office of the Director of National Intelligence warned that Iran, along with Russia and China, are all likely to interfere in the upcoming election and that Tehran had developed preference for the Democratic candidate, based on the perception that they would be less likely to increase tensions between the two countries.

The breach has raised concerns on Capitol Hill — where many recall Russia’s digital assault in 2016 where hackers stole and leaked emails belonging to Hillary Clinton’s presidential campaign and targeted voter registration databases in several states — about more potential foreign meddling ahead of November.

Rep. Eric Swalwell (CA), the top Democrat on the House Homeland Committee’s cybersecurity subpanel, publicly requested a briefing on the compromise on X, formerly known as Twitter.

A source familiar with the matter said the Cybersecurity and Infrastructure Security Agency (CISA) is preparing a briefing for lawmakers, though the timeline for when it will occur remains unclear.

A CISA spokesperson deferred comment to the FBI.