The FBI alerted other law enforcement agencies that QAnon adherents discussed acting as National Guard soldiers in Washington to try and infiltrate President-elect Joe Biden's inauguration, according to The Washington Post.
The FBI, in an intelligence report obtained by the newspaper, said it monitored individuals downloading maps of sensitive areas around Washington and talking about how those locations could be utilised to penetrate security, the Post reported.
The intelligence report warned that QAnon members and "lone wolves" indicated they plan to travel to Washington for Biden's swearing-in ceremony on Wednesday, the Post said.
"But the intelligence briefing did not identify any specific plots to attack the inaugural events" that would be similar to the January 6 insurrection on the US Capitol, which some QAnon members participated in, the Post said.
The FBI noted that it detected "suspicious traffic" on the communication systems used by some participants in the January 6 Capitol attack — but "nothing that points to any specific action," according to the Post.
The newspaper said the FBI declined to "characterise the credibility or gravity of the threats it outlined" in its briefing report.
The agency pointed the Post to comments made by FBI Director Christopher Wray last week, in which he said the FBI is seeing "extensive" chatter surrounding the inauguration and said "one of the real challenges in this space is trying to distinguish what is aspirational and what is potential".
"We're monitoring all incoming leads — whether calls for armed protests, potential threats that grow out of the January 6th breach of the Capitol or other kinds of potential threats leading up to Inaugural events and various other targets," Mr Wray said.
The Secret Service also declined to comment to the Post about the FBI's threat report, but told the newspaper that it "takes all threats seriously and will continue to work with our federal, state, local and military partners to continue securing the 59th Inauguration based on the relevant intelligence available to the security community."
CNN previously reported that the FBI is vetting the thousands of National Guard troops providing security at the inauguration ahead of their arrival in Washington in order to prevent any insider threats, and the US Army is working with the Secret Service to determine if there are soldiers who require additional background screening.
Acting Secretary of Defence Christopher Miller said on Monday that there is "no intelligence indicating an insider threat" to Biden's inauguration.
"We are leaving no stone unturned in securing the capital," Mr Miller said.
"The DC National Guard is also providing additional training to service members as they arrive in DC that if they see or hear something that is not appropriate, they should report it to their chain of command."
In the wake of the Capitol insurrection earlier this month, there has been a massive security presence in Washington for Biden's inauguration, with more than 20,000 National Guard troops expected in the city to help secure the event.