This story is part of, CNET's coverage of the voting in November and its aftermath.
Senior US officials said Wednesday that the government hasn't seen evidence of a coordinated effort to commit mail-in voting fraud, a claim President Donald Trump and some members of his administration have made for months.
At a briefing, intelligence officials who have been consulting with election workers across all 50 states said they haven't found evidence to support Trump's claims.
"We have not seen, to date, a coordinated national voter fraud effort during a major election," said a senior Federal Bureau of Investigation official, who spoke on background. "It would be extraordinarily difficult to change a federal election outcome through this type of fraud alone, given the range of processes that would need to be affected or compromised by an adversary at the local level."
The range of processes include being able to find every registered voter's address, forge their signatures, and replicating the barcodes and special stock the ballots are printed on.
The comments follow a series of statements by Trump, Attorney General William Barr and other members of the administration that foreign countries could print counterfeit ballots and sway the outcome of the US presidential election. Election experts and officials behind the process point out that mail-in voter fraud is nearly impossible to pull off.
Concerns over mail-in ballots have risen amid a surge in demand caused by the coronavirus outbreak. Several states have changed policies around absentee voting to protect public health and keep crowds to a minimum.
At the Wednesday briefing, the FBI official said the bureau has 56 field offices with agents and elections crimes coordinators frequently running through election fraud scenarios and working with local counties to safeguard mail-in ballots.
Officials at the Cybersecurity and Infrastructure Security Agency, a Department of Homeland Security branch that oversees election security, also said it hasn't seen any efforts from foreign actors to commit mail-in ballot fraud.
CISA officials said the agency is coordinating with election officials across the country to safeguard against cyberattacks. CISA sensors installed in local county networks have detected probes and scans for known vulnerabilities, but no significant attacks against election infrastructure.
"We have no information or intelligence that any nation-state threat actor is engaging any kind of activity undermining any part of the mail-in vote or ballots," said a senior CISA official, who also spoke on background.
The officials urged Americans to be patient for election results and vigilant for disinformation surrounding the election. The rise in mail-in ballots is expected to cause a delay in final results and several states will take as long as a week to count mail-in ballots.
There's still potential for disinformation campaigns, the officials said, adding that Russian, Chinese and Iranian efforts to affect election outcomes are ongoing. In early August, the Office of the Director of National Intelligence released a report stating that Russian campaigns are backing Trump while Chinese threat actors are pushing for the Democratic nominee Joe Biden.
"We encourage Americans to consume information with a critical eye," a senior official from the office of the Director of National Intelligence said on background. "Check out your sources before reposting messages."