CBS News has learned about a potential terror threat for the day before the election.
Sources told CBS News senior investigative producer Pat Milton that U.S. intelligence has alerted joint terrorism task forces that al Qaeda could be planning attacks in three states for Monday.
It is believed New York, Texas and Virginia are all possible targets, though no specific locations are mentioned.
U.S. authorities are taking the threat seriously, though the sources stress the intelligence is still being assessed and
its credibility hasn't been confirmed. Counterterrorism officials were alerted to the threat out of abundance of caution.
A senior FBI official told CBS News, "The counterterrorism and homeland security communities remain vigilant and well-postured to defend against attacks here in the United States. The FBI, working with our federal, state and local counterparts, shares and assesses intelligence on a daily basis and will continue to work closely with law enforcement and intelligence community partners to identify and disrupt any potential threat to public safety."
Intelligence about potential threats always increases during holiday seasons and when big events are approaching.
As Election Day nears, federal law enforcement is planning for several worst-case scenarios.
Earlier this week, an alert warned local police of "polling places" being seen as "attractive targets" for "lone wolf"-type attacks by individuals motivated by violent extremist ideologies, sovereign citizen or other extremist activity.
Comment: Could these new threats have anything to do with
Killary's 'Salvage Program'?
Reuters is reporting that the FBI's investigation of Russian interference in the U.S. presidential election extends to fake documents that suggest Hillary Clinton's campaign might take extreme measures like "staging civil unrest" to ensure she wins.
U.S. intelligence officials have warned privately that the Russian campaign to undermine the credibility of the election could move beyond hacking and leaking Democratic Party e-mails to posting fictional evidence of voter fraud or other disinformation, Reuters said.
The FBI reportedly is reviewing a seven-page electronic memorandum that was posted on Twitter on October 20 by Roger Stone, a Republican operative and former aide to Democrat Clinton's opponent Donald Trump, which carries the logos of the Clinton Foundation and Democratic pollster Joel Benenson's firm, the Benenson Strategy Group.
The memo, titled Salvage Program and identified as "fake" by the Clinton campaign and Clinton Foundation, claims her poll ratings had plunged and called for "severe strategy changes for November" that could include "staged civil unrest" and "radiological attack" with dirty bombs to disrupt the November 8 vote.
It is not clear where the fraudulent document originated or how it started circulating on the Internet.
When he linked to the document on Twitter, Stone wrote: "If this is real: OMG!!"
Stone on November 4 tweeted that he received the document in an e-mail and linked to an article that said the fake document came from the hacking group Anonymous.
Stone called the Reuters story about the document a "witchhunt."
Reuters reported that another fake document -- a letter supposedly written by Democratic Senator Tom Carper -- also suggests that the Democratic Party would go to extreme lengths to ensure it wins the election.
In the letter, which Carper's office identified as fake, the senator writes to Clinton that "we will not let you lose this election," Reuters said.
In full swing. It would be funny if it wasn't tragic.