WASHINGTON -- The FBI said Monday it is investigating allegations that sensitive documents from the Trump campaign were stolen in a cyber intrusion days after the campaign declared it had been hacked by Iran.

The FBI released a brief statement reading, 鈥淲e can confirm the FBI is investigating this matter.鈥

The Trump campaign provided no specific evidence of Iran鈥檚 involvement, but the claim came shortly after Microsoft issued a report detailing foreign agents鈥 attempts to interfere in the U.S. campaign in 2024. The report cited an instance of an Iranian military intelligence unit in June sending 鈥渁 spear-phishing email to a high-ranking official of a presidential campaign from a compromised email account of a former senior advisor.鈥

Two people familiar with the matter said the Biden-Harris campaign was also targeted in the suspected Iranian cyber intrusion that is under FBI investigation. The people spoke on the condition of anonymity because they were not authorized to discuss the details of the investigation.

Politico reported Saturday that it began receiving emails on July 22 from an anonymous account. The source 鈥 an AOL email account identified only as 鈥淩obert鈥 鈥 passed along what appeared to be a research dossier the campaign had apparently done on the Republican vice presidential nominee, Ohio Sen. JD Vance. The document was dated Feb. 23, almost five months before Trump selected Vance as his running mate.

鈥淭hese documents were obtained illegally鈥 and 鈥渋ntended to interfere with the 2024 election and sow chaos throughout our Democratic process,鈥 Trump campaign spokesperson Steven Cheung said.

At least three staffers in the Biden-Harris campaign were targeted with phishing emails, but investigators have uncovered no evidence the attempt was successful, one of the people said. The attempts came before U.S. President Joe Biden dropped out of the race.

Trump

The FBI began investigating that cyber incident in June and intelligence officials believe Iran was behind the attempts, that person said. Officials have also been in touch with tech companies in recent months about the possibility that people linked to the Trump and Biden-Harris campaigns were being targeted through email.

Harris' campaign said in a statement, 鈥淥ur campaign vigilantly monitors and protects against cyber threats, and we are not aware of any security breaches of our systems.鈥 It declined to address whether it had identified any state-based intrusion attempts.

Iran鈥檚 mission to the United Nations, when asked about the claim of the Trump campaign, denied being involved.

However, Iran long has been suspected of running hacking campaigns targeting its enemies in the Middle East and beyond. Tehran also long has threatened to retaliate against Trump over the 2020 drone strike he ordered that killed prominent Revolutionary Guard Gen. Qassem Soleimani.

In its report, Microsoft stated that 鈥渇oreign malign influence concerning the 2024 US election started off slowly but has steadily picked up pace over the last six months due initially to Russian operations, but more recently from Iranian activity.鈥

The analysis continued: 鈥淚ranian cyber-enabled influence operations have been a consistent feature of at least the last three U.S. election cycles. Iran鈥檚 operations have been notable and distinguishable from Russian campaigns for appearing later in the election season and employing cyberattacks more geared toward election conduct than swaying voters.鈥

鈥淩ecent activity suggests the Iranian regime 鈥 along with the Kremlin 鈥 may be equally engaged in election 2024,鈥 Microsoft concluded.