Tributes poured in for longtime Democrat California Sen. Dianne Feinstein, who passed away Thursday evening at the age of 90.

Fox News confirmed Feinstein's passing and was told flowers were placed on the late senator's desk Friday morning.

Senate Majority Leader Chuck Schumer, D-N.Y., said it is "a very, very sad day for all of us" and announced he would be speaking at 10 a.m.

DIANNE FEINSTEIN DEAD: LONGTIME CALIFORNIA SENATOR WAS 90

Dianne Feinstein

San Francisco Mayor Dianne Feinstein smiling while working in her office. (Getty Images)

Sen. Dick Durbin, D-Ill., said Feinstein was his "friend and my seatmate on the Senate Judiciary Committee for over 20 years."

"She was always the lady, but she never backed down from a cause that she thought was right," Durbin said. "She has written a great record in areas like the assault weapons ban, violence against women and so many other areas."

"We've lost one of the real leaders in the Senate," he added.

Dianne Feinstein

The swearing-in of Dianne Feinstein at the Senate. (Jeffrey Markowitz/Sygma via Getty Images)

Sen. John Kennedy, R-La., said in a press release that Feinstein "cared about her country and her state."

"We didn’t agree politically, but she was a delight to serve with. I so valued our friendship and am praying for all of her loved ones," Kennedy said.

Oklahoma Rep. Tom Cole, the Republican chairman of the House Rules Committee, observed a moment of silence for the departed senator during a committee hearing Friday morning.

"I know many of us had the opportunity to deal with her and certainly all of us on both sides now respect her," Cole said.

"I would ask that, before we proceed, that we observe a moment of silence in recognition and memory of our colleague on the other side of the Rotunda," he continued.

Senator Dianne Feinstein

Senator Dianne Feinstein, a Democrat from California, is pictured during a Senate Intelligence Committee nomination hearing in Washington, D.C., on Wednesday, July 12, 2023. (Al Drago/Bloomberg via Getty Images)

Sen. Chuck Grassley, the longtime Republican senator from Iowa, wrote that Feinstein "did an outstanding job representing the [people] of California."

"I worked closely [with] her as a member of the drug caucus [and] judiciary [committee,] Grassley posted on X, formerly Twitter.

"During the time I was chair [and] she was ranking Democrat we had a wonderful working relationship," Grassley continued. "She’s a true public servant I’ll miss her."

Sen. Marco Rubio, R-Fla., wrote, "Senator Feinstein was a political pioneer with a historic career of public service."

"Intelligent, hard working [and] always treated everyone with courtesy [and] respect," Rubio posted on X. "May God grant her eternal rest."

Rep. Katie Porter, D-Calif., posted that Feinstein "was a trailblazer for women in California politics, and her leadership on gun violence prevention and anti-torture made our nation more just."

"I wish her loved ones strength during this difficult time," she wrote.

"Senator Dianne Feinstein was a champion for Gun Violence Prevention that broke barriers at all levels of government," Rep. Maxwell Frost, D-Fla., posted.

"We wouldn’t have had an assault weapons ban if it wasn’t for Senator Feinstein and due to her tireless work, we will win it back," he continued. "May her memory be a blessing."

Tributes to Feinstein continued to roll in from across the aisle after her passing.

The longtime senator had suffered from extensive health issues for more than a year, leading many to wonder about her fitness for office.

Feinstein was present in the Senate on Wednesday and cast a vote at 11:45 a.m. ET, according to the congressional record. 

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However, she missed two votes later in the afternoon. 

Feinstein, the longest-serving female senator, was first elected to the role in 1992.

Fox News Digital's Chris Pandolfo, Greg Norman, Chad Pergram and Anders Hagstrom contributed reporting.