Former FBI Director James Comey on Thursday testifying before the Senate Intelligence Committee in Washington. REUTERS/Jim Bourg

James Comey declined to answer in an open setting whether the FBI verified any of the criminal allegations in the Steele dossier

Experts say this may mean there's truth to the document, though they caution against jumping to conclusions

The dossier puts intelligence officials in a difficult situation

Former FBI Director James Comey may have hinted during his testimony before the Senate Intelligence Committee on Thursday that some of the allegations in the now-infamous Trump-Russia dossier may have been verified.

The dossier, compiled by a former MI6 intelligence officer named Christopher Steele, detailed several allegations of collusion between Donald Trump's 2016 presidential campaign and Russia, among other salacious details. The FBI is investigating the explosive claims made in the dossier.

During his testimony, Comey was asked by Sen. Richard Burr, the Republican chairman of the Senate Intelligence Committee, whether the FBI was able to confirm any criminal allegations contained in the document.

Comey replied that he couldn't answer the question in an "open setting," because it "goes into the details" of the FBI's investigation.

Some experts say the fact Comey didn't publicly comment on the criminal allegations in the dossier indicates some of the facts in the document could be verified.

BuzzFeed first published the full dossier in January.

Andy Wright, a former associate counsel to President Barack Obama who is now a professor at Savannah Law School, said it was "striking" that Comey said he would need to answer questions about the veracity of the Steele dossier in a closed session.

"That could mean some dossier facts were verified," Wright said. "It could also mean that the sources for his state of knowledge were classified."

Comey with President Donald Trump during an Inaugural Law Enforcement Officers and First Responders Reception in the Blue Room of the White House on January 22. Pool/Andrew Harrer via Getty Images

Claire Finkelstein, a professor at the University of Pennsylvania's law school, told Business Insider that Comey's comments during his testimony weren't the first indicator "that there is actual intelligence" in the dossier.

"On several occasions in his testimony, he has said, 'I could not answer that in an open session,' indicating that there's quite a bit more that he knows, of a classified nature, that he can't discuss," she said.

Finkelstein said Steele, who compiled the document as part of political opposition research, was a "reputable" agent, even though the document came stripped of any information that could identify sources.

"So it is my expectation that the details of that dossier will be confirmed through the investigation of Mr. Mueller," she added. Robert Mueller was appointed as a special counsel to investigate whether Russia colluded with the Trump campaign to meddle in the election. Previously, Attorney General Jeff Sessions recused himself from the investigation after undisclosed conversations between him and Russia’s ambassador to the US came to light.

Glenn Carle, a CIA veteran and former spy, said "virtually every point" of Steele's dossier had been substantiated, "point after point after point."

"The involvement of Russian intelligence with members of Trump's entourage, and with Trump at the very least through financial 'hooks,' is glaring for a professional intelligence officer," Carle said.

As a former intelligence officer, Carle said he was "99.8%" confident in the Steele dossier.

He pointed to what he called a "perverse proof-by-murder" in which one of Steele's "interlocutors" wound up dead after he was publicly named.

A demonstrator with a sign of Vladimir Putin during an anti-Trump rally on Saturday in New York City. Eduardo Munoz Alvarez/Getty Images

Oleg Erovinkin, a former KGB general who was suspected of helping Steele compile the dossier, was found dead in his car in Moscow in December under dubious circumstances, The Telegraph reported. Experts told The Telegraph that Erovinkin may have been a key source Steele referred to in his dossier.

Sergei Mikhailov, the head of the Federal Security Service, a Russian intelligence agency, was also arrested in January after American officials said they believed he was involved with election hacking, The New York Times reported. Novaya Gazeta, an independent Russian newspaper, reported that a bag was thrown over his head and he was marched to an undisclosed location.

Carle detailed what he said was an "excruciating dilemma" for intelligence officers regarding the allegations contained in Steele's dossier.

"It's beyond the Steele dossier: It is about being alarmed that the president and his lieutenants are betraying their oaths," he said.

"Comey is being careful," Carle said. "The report is spot on."

Robert Dietz, a former top lawyer at the CIA and National Security Agency, cautioned that he didn't think "one could take much" from Comey's comments during the testimony. Dietz said he didn't "share the view" that Comey implied that the FBI had confirmed allegations in the Steele dossier, based on the short exchange.

Comey said during his testimony he thought Trump fired him on May 9 "because of the Russia investigation." Comey continued his testimony in a closed session with Senators on Thursday.