Washington (CNN) The FBI has been conducting multiple investigations of alleged connections between Russia and Donald Trump, his presidential campaign or its backers. But none so far have yielded proof of criminal connections between the parties.

US law enforcement and intelligence officials investigating hacks of Democratic Party organizations view Russian spy agencies as trying to sow chaos and confusion in the US elections, but not necessarily trying to help a particular candidate.

The US government has publicly accused senior levels of Russian government of being behind hacks on Democratic groups and the release of sensitive documents online. The accusations including meddling in the 2016 election.

But the government has stopped short of accusing Russia of trying to swing the election in a particular direction, and has also not formally accused Moscow of involvement in a hack of Hillary Clinton campaign chairman John Podesta or of attempts to hack voter registration databases that have been detected.

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The FBI has kept a close lid on any information related to its investigation of Moscow's connection to the Trump campaign. Democrats are crying foul, since the FBI has made public in the campaign's final days that it is reviewing new emails related to its investigation of Hillary Clinton's use of a private email server while secretary of state. The additional emails were uncovered in a separate investigation into Anthony Weiner, estranged husband of top Clinton aide Huma Abedin, in connection to a sexting scandal.

As CNN first reported, the FBI has been examining for well over a year allegations about former Trump campaign chairman Paul Manafort and his firm and their connections to pro-Putin figures in Ukraine. That probe has also touched on other lobbying firms in Washington that were involved in Ukraine political work -- including the Podesta Group, the firm of Tony Podesta, brother of John Podesta.

The FBI also has looked into alleged meetings former Trump adviser Carter Page had in Russia related to individuals under US sanctions. Among those who suggested the FBI investigate this possible connection was Sen. Harry Reid, the chamber's Democratic leader, who has made public a letter he sent to the FBI on the matter. So far the investigation hasn't yielded much beyond the initial claim.

Page has denied any connection, blaming Democrats for raising the issue.

"That is just so false that I don't even know where to begin," Page told CNN. "Again, most of the accusations that have come have been sort of a downward circle ... bouncing back and forth between media accounts and stories that are planted ... by the Clinton campaign against me."

The FBI is also looking into allegations against Roger Stone, a Trump supporter, about a possible connection to WikiLeaks, which has been undergoing a complex six-year investigation.

The accusations against Stone hinge on Democrats' claims that he conspired with WikiLeaks' Julian Assange to coordinate the distribution of hacked emails from Democratic Party officials. In one case, a Stone tweet foreshadowed damaging information for Clinton's campaign coming from WikiLeaks.

Stone told NBC News in October that he and Julian Assange have a "mutual friend" and said he has "back-channel communications with WikiLeaks" but denied accusations he's conspiring or coordinating with WikiLeaks.

"They certainly don't clear or tell me in advance what they're going to do," he said.

WikiLeaks has been releasing thousands of emails hacked from Podesta's private email account daily for more than three weeks. While Russia and WikiLeaks have denied any coordination, a private security firm has linked the same Russian hackers who broke into the DNC to a phishing email received by Podesta.

The FBI and Justice Department have encountered difficulties with the WikiLeaks investigation in part because of First Amendment protections for the website's publication of emails it has received. Receiving and disseminating hacked materials is similar to what news organizations do.

The FBI so far hasn't been able to prove that WikiLeaks is conspiring with Russian intelligence to steal materials. WikiLeaks refuses to make public its sources.

Democrats cry foul on Comey

Since FBI Director James Comey notified members of Congress on Friday that the bureau had discovered emails on one of Weiner's electronic devices that could be relevant to the Clinton server investigation, Democrats have accused him of political motivations.

Reid has intimated without evidence that the FBI is concealing information that would link Trump and Russia, and other Democrats are disputing the idea that Russia is not trying to tip the scales for Trump.

"You have to be willfully blind to say Russia is not trying to help one side over the other," California Rep. Adam Schiff, the senior Democrat on the House intelligence committee, told CNN. "The leaks speak for themselves. They are uniformly damaging Clinton, not Trump. And it's an effort to damage one candidate's campaign and American democracy."

But sources told CNN that at no point did Comey attempt to withhold publicly naming Russia as behind of election related hacks to avoid influencing the election, as some media reported.

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Comey did at one point broach with a smaller group of administration officials concerns with naming Russia but for other reasons, the sources added. One was that the FBI was working with the Russian authorities on various criminal cases and arrests and they did not want to compromise those investigations.

Additionally, US investigators were not yet ready to make a specific link between the Russian spy services and WikiLeaks.

But at no time, according to sources, did Comey mention the election as being a contributing factor to his reticence. And the White House was opposed to naming Russia, as CNN previously reported, in part because of concern about the election and appearing to show favoritism.

By the time Russia was publicly named as the culprits by the government, top FBI cyber officials as well as Comey were not opposed to the move, according to the officials.

In the end, the statement pointing to Russia came from the Office of the Director of National Intelligence, not the FBI.