Jeffrey Epstein's apparent suicide Saturday morning in a federal jail launched new conspiracy theories online in a saga that has provided fodder for them for years, fueled by Epstein's ties to princes, politicians and other famous and powerful people.

Online theorists Saturday quickly offered unsubstantiated speculation — including some retweeted by President Trump — that Epstein's death wasn't a suicide, or it was faked. Mr. Trump's retweet of conservative commentator Terrence K. Williams continued to reverberate, drawing bipartisan ire from members of the Senate Intelligence Committee who said the president was playing directly into Kremlin interests.

Republican Sen. Marco Rubio of Florida said Russia bots and trolls had seized on the conspiracy theory and spread it online in an effort to pit Americans against one another. "It's sad (and frightening) to see so many Americans on both sides of partisan unwittingly helping them. Putin has weaponized our polarization," he tweeted, without naming the president.

Get Breaking News Delivered to Your Inbox

Rachel Cohen, a spokesperson for Sen. Mark Warner of Virginia, the top Democrat on the committee, concurred with Senator Rubio's assessment and called it "astonishingly irresponsible for the President to be echoing these charges."

Cohen said spreading the conspiracy theory amounted to "doing Russia's dirty work for them."

Conspiracy chatter picked up on the conjecture that resurged after Epstein's July 6 arrest on allegations that he orchestrated a sex-trafficking ring designed to bring him teenage girls. Some of his accusers have described being sexually abused by the wealthy financier's friends and acquaintances.

The combination created fertile ground for theories and misinformation to breed on social media sites such as Facebook, Twitter and YouTube.

Epstein, 66, had been denied bail and faced up to 45 years behind bars on federal sex trafficking and conspiracy charges unsealed last month. He had pleaded not guilty and was awaiting trial next year.

His relationships with Mr. Trump, former President Bill Clinton and Britain's Prince Andrew were at the center of those online rumors and theories, many of which question what politicians knew about Epstein's alleged sex crimes.

Others theories, however, have been easily debunked.

For example, days after his arrest online memes and Facebook statuses wrongly claimed the Obama administration, in order to protect Mr. Clinton, forged a once-secret deal in 2008 in Florida that allowed him to plead guilty to soliciting a minor for prostitution to avoid more serious charges. The deal was actually executed before President Barack Obama took office, under former President George W. Bush.

Meanwhile, a manipulated photo, shared by thousands on Twitter and Facebook, falsely claimed to show Epstein with Mr. Trump and a young Ivanka Trump, the president's daughter.

Both Mr. Clinton and Mr. Trump have denied being privy to Epstein's alleged scheme.

Other Epstein theories floating online have been darker, especially after Epstein was found injured on the floor of his cell last month with bruises on his neck. Some online commentators described it as a "murder attempt."

Hours after Epstein's death Saturday, as the hashtag #EpsteinMurder was trending worldwide on Twitter, the president joined Twitter speculation around Epstein's death while under the federal government's watch.

Mr. Trump, who rose to conservative prominence by falsely claiming Obama wasn't born in the U.S., retweeted unsubstantiated claims about Epstein's death.

When asked on "Fox News Sunday" about the president's retweet, White House counselor Kellyanne Conway said, "I think the president just wants everything to be investigated."

Other politicians also took to social media to question the circumstances.

Republican Sen. Rick Scott of Florida — the state where some of Epstein's alleged sexual abuse crimes took place — suggested the possibility that others might have been involved in Epstein's death when he called on corrections officials to explain what happened at the Metropolitan Correctional Center in Manhattan.

The victims of Epstein’s heinous actions deserved an opportunity for justice. Today, that opportunity was denied. The Federal Bureau of Prisons must provide answers on what systemic failures of the MCC Manhattan or criminal acts allowed this coward to deny justice to his victims. — Rick Scott (@SenRickScott) August 10, 2019

Former Mayor Rudy Giuliani, now an attorney for Mr. Trump, tweeted out several questions about Epstein's death.

"Who was watching? What does camera show? ... Follow the motives" Giuliani tweeted Saturday afternoon.

The FBI and the Department of Justice's Office of the Inspector General will investigate the circumstances surrounding Epstein's death, Attorney General William Barr said.

"Mr. Epstein's death raises serious questions that must be answered," Barr said in a news release.

Epstein's suicide was likely recorded by jail cameras, according to Preet Bharara, the former federal prosecutor in Manhattan.

"One hopes it is complete, conclusive, and secured," Bharara tweeted.

Jeffrey Epstein, seen in a March 28, 2017, image provided by the New York State Sex Offender Registry. New York State Sex Offender Registry via AP

Epstein's arrest in July launched separate investigations into how authorities handled his case initially when similar charges were first brought against him in Florida more than a decade ago. U.S. Labor Secretary Alexander Acosta resigned last month after coming under fire for overseeing that deal when he was U.S. attorney in Miami.

Epstein's lawyers maintained that the new charges in New York were covered by the 2008 plea deal and that Epstein hadn't had any illicit contact with underage girls since serving his 13-month sentence in Florida.