British government spies were reportedly the first to inform U.S. intelligence officers of the alleged connections between the Russian government and President Donald Trump's campaign.
Britain's intelligence agency, GCHQ, learned of the potential ties as early as the end of 2015, according to an April 13 report from The Guardian. Between then and summer 2016, the U.S. learned similar details from other western countries, including Germany, Estonia, Australia and Poland, said one source, while another said that the General Directorate for External Security of France and the Netherlands played a significant role in that process.
"They now have specific concrete and corroborative evidence of collusion," a source told The Guardian. "This is between people in the Trump campaign and agents of [Russian] influence relating to the use of hacked material."
But according to the report, the multiple probes into the matter got off to a slow start.
Despite the tip from the British agency, shared during routine briefings, the FBI and CIA were slow to delve into the information, as American agencies are "trained not to" look through citizens' private communications if there is no warrant, said a source who called GCHQ the "principal whistleblower."
"It looks like the [U.S.] agencies were asleep," the source explained. "[The European agencies] were saying: 'There are contacts going on between people close to Mr. Trump and people we believe are Russian intelligence agents. You should be wary of this.'"
The overall message was that something was "not right."
In summer 2016, GCHQ then passed on all of the information to CIA head John Brennan, who escalated the matter and launched the investigation.
In March, FBI Director James Comey revealed that his bureau was joining the CIA in starting its own probe on the matter.
"I have been authorized by the Department of Justice to confirm that the FBI, as part of our counterintelligence mission, is investigating the Russian government's efforts to interfere in the 2016 presidential election," Comey told members of Congress on March 20, according to NPR. "And that includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government and whether there was any coordination between the campaign and Russia's efforts. As with any counterintelligence investigation, this will also include an assessment of whether any crimes were committed."
It is not known which particular members of Trump campaign, if any, intelligence officers believe colluded with Russia, according to The Guardian.