WASHINGTON — The CIA received intelligence last summer indicating Donald Trump’s campaign aides were in contact with Russian government officials, information that was worrisome enough to pass to the FBI for investigation, former CIA Director John Brennan said Tuesday.

Brennan said it wasn’t clear at the time if the Trump aides were acting as Russian agents or if the “contacts and interactions” were routine and unconnected to a larger effort by Russian intelligence agencies to influence the outcome of the 2016 election.

Brennan’s first public accounting since he stepped down in January shed new light on the political scandal that has dogged President Donald Trump since before he took office and that now has spawned separate investigations by the FBI, four congressional committees, the Pentagon and a Virginia grand jury.

“I encountered and am aware of information and intelligence that revealed contacts and interactions between Russian officials and U.S. persons involved in the Trump campaign that I was concerned about,” Brennan told the House intelligence committee.

He said the intelligence “raised questions in my mind whether the Russians were able to gain the cooperation of those individuals.”

Brennan revealed that the U.S. government concerns about possible collusion were deeper than previously known and involved multiple contacts. He also made clear that the unease began long before the intelligence community publicly disclosed a joint conclusion in January, shortly before Trump’s inauguration, that Moscow had sought to help Trump win.

At a separate Senate Armed Services Committee hearing Tuesday, Director of National Intelligence Dan Coats refused to confirm or deny a Washington Post report that the president asked him in March to publicly deny the existence of any evidence of collusion between the Trump campaign and Russia.

“On this topic, as well as other topics, I don’t feel it’s appropriate to characterize discussions and conversations with the president,” Coats said.

Trump reportedly made the same request to Adm. Mike Rogers, director of the National Security Agency. Both men, the report said, refused to comply with Trump’s request, which they both deemed inappropriate. The White House has declined comment.

The leaders of the Senate intelligence committee said Tuesday they were sending subpoenas to former national security adviser Michael Flynn’s businesses, the Flynn Intel LLC and Flynn Intel Inc., seeking documents related to dealings with Russia before the election.

The move comes a day after Flynn’s lawyers refused to comply with a previous committee subpoena sent directly to the retired three-star Army general, citing his constitutional protection against self-incrimination.

Sen. Richard Burr, R-N.C., the committee chairman, and Sen. Mark Warner, D-Va., the vice chairman, said they were issuing new subpoenas because companies can’t invoke the 5th Amendment.

Burr said the committee could recommend Flynn be charged with contempt of Congress for his refusal to comply with the original subpoena.

Brennan said he personally warned Russia to stop meddling in the U.S. campaign in an Aug. 4 telephone conversation with Gen. Alexander Bortnikov, the head of the Federal Security Service, Russia’s primary spy service.

Brennan said he told Bortnikov that the Russian operation, which involved hacking and leaking thousands of Democratic Party emails, “would be certain to backfire” because its disclosure would outrage Americans.

“It should be clear to everyone Russia brazenly interfered in our 2016 presidential election process and that they undertook these activities despite our strong protests and explicit warning that they do not do so,” Brennan said.

In addition to alerting the FBI last summer, which is responsible for counterintelligence investigations, Brennan said he created a special unit in the CIA to monitor and analyze intelligence about Russia’s interference in the election.

He said he also briefed senior members of Congress in August and September on the Russian meddling.

Rep. Trey Gowdy, R-S.C., pressed Brennan on whether there was “evidence of collusion” between Moscow and the Trump campaign.

“I don’t know whether or not such collusion — and that’s your term — such collusion existed,” Brennan answered. “I don’t know. But I know that there was a sufficient basis of information and intelligence that required further investigation by the [FBI] to determine whether or not U.S. persons were actively conspiring, colluding with Russian officials.”

david.cloud@latimes.com