Federal prosecutors have secured criminal charges against multiple Iranian hackers for allegedly targeting members of former President Donald Trump's presidential campaign as part of a malicious cyber scheme, multiple sources familiar with the investigation confirmed to CBS News.

The Iranian hackers were indicted by a grand jury on Thursday and the charges could be announced as early as Friday, the sources said. The nature of the allegations and the names of the defendants were unknown as charging documents remain under seal. The exact number of people charged was also not confirmed.

ABC News and Politico first reported on elements of the charges.

A Justice Department spokesperson declined to comment on CBS News' reporting. A spokesperson for the Trump campaign also did not immediately respond to a request for comment.

Once publicly announced, the charges will mark an escalation in the federal government's work to combat Iran's alleged efforts to interfere in the 2024 presidential election. Federal officials have warned Iran is seeking to undermine Trump's campaign.

The FBI launched probes earlier this summer after both the Trump and then-Biden campaigns experienced attempted phishing schemes targeting people associated with the candidates, sources told CBS News in August.

Last week, federal officials with the FBI and other intelligence agencies released a statement confirming, "Iranian malicious cyber actors in late June and early July sent unsolicited emails to individuals then associated with President Biden's campaign that contained an excerpt taken from stolen, non-public material from former President Trump's campaign as text in the emails. There is currently no information indicating those recipients replied."

The statement went on to say that "Iranian malicious cyber actors have continued their efforts since June to send stolen, non-public material associated with former President Trump's campaign to U.S. media organizations…Foreign actors are increasing their election influence activities as we approach November."

Iran's United Nations mission previously denied it had plans to interfere or launch cyberattacks in the U.S. presidential election, telling CBS News in a statement last week that "the Islamic Republic of Iran does not engage in the internal uproars or electoral controversies of the United States," adding that "Iran neither has any motive nor intent to interfere in the U.S. election; and, it therefore categorically repudiates such accusations."

Trump's campaign revealed last month that it had been hacked and said Iranian actors were involved in stealing and distributing sensitive internal documents to members of the press.

FBI agents worked with both Google and Microsoft — two major tech firms and providers of email services — to dig into the apparent spearphishing attacks targeting those close to both presidential campaigns, according to two people familiar with the probe. A report published by Microsoft earlier this summer revealed Iran is evolving its tactics to affect the upcoming election.

Trump and former members of his administration have been increased targets of Iranian actors following the killing of Iranian military commander Qassem Soleimani in 2020. Some former officials received increased protection because of death threats, and in July, federal prosecutors filed charges against a Pakistani national with ties to Iran for allegedly planning to assassinate American politicians, including possibly Trump.

Iran is not the only foreign adversary that U.S. officials say is seeking to undermine the upcoming presidential election. Intelligence agencies have warned Russia and China have launched cyber campaigns of their own to sew chaos, with Russia allegedly seeking to damage Vice President Kamala Harris' bid for the White House.

Speaking at an event hosted by the Atlantic Council on Thursday, Deputy Attorney General Lisa Monaco said, "We are seeing more threat actors, more threat actors getting into the game" of election interference, exacerbated by advancements in artificial intelligence.

The goal, according to Monaco, is to "sow discord, sow distrust in our election system and undermine confidence in our democratic process."

and contributed to this report.