United States authorities received intelligence from a source in recent weeks on an Iranian plot to assassinate Donald Trump, which has led the Secret Service to increase security around the former president, multiple individuals briefed on the subject told CNN.

There is no indication that Thomas Matthew Crooks, the would-be assassin who attempted to kill the former president on Saturday, was linked to the plot, the sources added.

The existence of the intelligence threat from a hostile foreign intelligence agency — and the enhanced security for Trump — raises new questions about the security lapses at the Saturday rally and how a 20-year-old man managed to access a nearby rooftop to fire shots that injured the former president.

A US national security official said the Secret Service and Trump campaign were made aware of the threat before Saturday’s rally.

“Secret Service learned of the increased threat from this threat stream,” the official told CNN. “NSC (National Security Council) directly contacted USSS (United States Secret Service) at a senior level to be absolutely sure they continued to track the latest reporting. USSS shared this information with the detail lead, and the Trump campaign was made aware of an evolving threat. In response to the increased threat, Secret Service surged resources and assets for the protection of former President Trump. All of this was in advance of Saturday.”

The Trump campaign would not disclose whether it was made aware of the Iran threat. “We do not comment on President Trump’s security detail. All questions should be directed to The United States Secret Service,” the campaign said in a statement.

The Secret Service recently “added protective resources and capabilities to the former president’s security detail,” agency spokesperson Anthony Guglielmi said in a statement on Sunday.

Secret Service officials have warned the Trump campaign repeatedly against holding outdoor rallies, which pose bigger risks than events to which the agency can properly control access, people briefed on the matter said.

The FBI, which is conducting the investigation into Saturday’s shooting, declined to comment on the matter.

NSC spokesperson Adrienne Watson said there is no known connection between the shooter and any other person or entity at the moment.

CNN has requested comment from the Department of Homeland Security and the Iran’s Permanent Mission to the United Nations.

Iran has repeatedly vowed to avenge the US killing of Qasem Soleimani, the commander of the Iranian military’s Islamic Revolutionary Guard Corps (IRGC), in January 2020.

In August 2022, the Justice Department announced criminal charges against a member of the IRGC for allegedly trying to plot the assassination of John Bolton, who served as Trump’s national security adviser. US prosecutors stated that the plot against Bolton was “likely in retaliation” for Soleimani’s assassination.

Former Secretary of State Mike Pompeo was also a target of the Iranian assassination plot, according to a federal law enforcement source familiar with the investigation, and a source close to Pompeo.

For months, law enforcement officials have been concerned about the persistent threat of Iran potentially attempting to assassinate former Trump officials and the former president himself, according to multiple sources familiar with the matter. But the recent intelligence suggested a significant threat increase, the sources told CNN.