Former President Barack Obama warned President Donald Trump about hiring retired Army Lt. Gen. Michael Flynn during a meeting in November 2016, NBC and CNN reported Monday.

NBC reports the warning came days after Trump defeated Democratic presidential nominee Hillary Clinton in the presidential election. During a 90-minute discussion in the Oval Office, Obama cautioned Trump about hiring Flynn, who was later brought on as national security adviser.

NBC’s Peter Alexander tweeted the White House’s reaction to the claims:

BREAKING: Trump WH's first reaction to NBC exclusive that Pres Obama warned Trump against hiring Flynn last November during Oval Ofc mtg. pic.twitter.com/duqrdqJ7V2 — Peter Alexander (@PeterAlexander) May 8, 2017

Earlier on Monday, Trump attacked Obama for giving Flynn security clearance. Obama fired Flynn from his position as head of the Defense Intelligence Agency in his administration in 2014 over reported leadership clashes.

During his daily press briefing Monday, White House press secretary Sean Spicer said that “it’s true President Obama made it known he wasn’t exactly a fan of Gen. Flynn’s,” but questioned why Obama didn’t suspend Flynn’s security clearance.

Spicer said Trump “stands by” the decision to ask Flynn to resign in February, which happened after it was reported Flynn had discussed U.S. sanctions against Russia with that country’s ambassador in the weeks before Trump’s inauguration.

News of Obama’s warning broke just hours before former acting Attorney General Sally Yates was scheduled to testify in front of the Senate on the Trump campaign’s ties to Russia. According to multiple media outlets, Yates had also tried to warn the White House about Flynn.

Trump fired Yates in January, after she refused to defend his controversial executive order on Muslim immigration.

This post has been updated with the White House’s response, Spicer’s comments from Monday’s press briefing and more details on Flynn’s time in the Obama administration.