The FBI reportedly warned then-Republican presidential nominee Donald Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE in the months before the election that Russia and other foreign adversaries would probably try to infiltrate his presidential campaign.

Multiple government officials told NBC News that senior FBI officials briefed both Trump and Democratic presidential candidate Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE about the threats, which it said are commonly offered to major party nominees for the White House.

The briefings, the officials told NBC, are used to alert candidates and their teams about such threats. They are generally given around the point at which candidates begin receiving classified information, and campaigns are told to alert any suspicious activity to authorities.

A White House official downplayed the news, saying there was nothing unusual about the briefings.

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"That the Republican and Democrat nominee for President received a standardized briefing on counter-intelligence is hardly a news story," White House spokesman Raj Shah told NBC. "That NBC News hears about the contents of this classified conversation due to an inappropriate leak is a news story."

The U.S. intelligence community has concluded that Russia interfered in last year's presidential election with the goal of hurting Clinton's campaign and helping Trump's.

That has led to numerous congressional probes of the election, and an investigation by special counsel Robert Mueller that was kickstarted by Trump's decision to fire FBI Director James Comey in May.

Trump has repeatedly insisted that there was no collusion between his campaign and Russia.

Four people have been indicted so far in Mueller’s probe, including former national security adviser Michael Flynn and former campaign aide George Papadopoulos, who both pleaded guilty to lying to the FBI about their contacts with Russians.

The first briefing by the FBI for Trump officials took place in August 2016, according to NBC. That was about two months after a Russian lawyer met with Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE at Trump Tower prompted by an email promising damaging information about Clinton. Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE and Jared Kushner Jared Corey KushnerAbraham Accords: New hope for peace in Middle East Tenants in Kushner building file lawsuit alleging dangerous living conditions Trump hosts Israel, UAE, Bahrain for historic signing MORE, Trump's son-in-law, sat in on the meeting.

Manafort has also been indicted in the Mueller probe.

Other campaign contacts with Russia or Russia-linked groups occurred after the reported briefing, including Donald Trump Jr.’s Twitter exchange with WikiLeaks and then-Sen. Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE’s (R-Ala.) meeting with then-Russian Ambassador Sergey Kislyak, though it is unclear if any of the Trump officials thought there was anything suspicious about the contacts.