The FBI said in a statement that they are aware of bomb threats in "several states" and "many of which appear to originate from Russian email domains."

"None of the threats have been determined to be credible thus far," the FBI said.

Earlier, Georgia Secretary of State Brad Raffensperger said a series of bomb threats in Fulton County appeared to come from Russia, but did not explain further.

"As always, we urge the public to remain vigilant and report suspicious activity to state or local law enforcement, or submit tips to the FBI at 1-800-CALL-FBI (1-800-225-5324) or online at tips.fbi.gov," the agency said.

-ABC News' Luke Barr and Pierre Thomas

Representatives from the nation's largest voter help hotline echoed what ABC News heard from state election officials in the battlegrounds: So far, so good. There have been no major disruptions or other issues beyond isolated, garden-variety episodes, the hotline said.

The Election Protection Hotline (1-866-OUR-VOTE) is run by the nonpartisan Lawyers Committee for Civil Rights Under Law and is staffed by 4,776 volunteer lawyers across 50 states. ABC News has profiled and embedded with this service in previous elections.

As of noon ET, the hotline has received 6,000 calls from voters. The majority of the calls have come in from Pennsylvania, North Carolina, Florida and Michigan.

Most of those were reporting frustration with long lines, delays in polling place opening, or difficulty using electronic voting machines.

So far, organizers have seen no widespread episodes of violence or intimidation.

The longest lines tracked by hotline are in Florida, Michigan and Pennsylvania, particularly near college campuses. Legal teams are seeking voting extensions at select polling places in Georgia, Illinois and Kentucky, where there were delays in opening this morning -- but nothing out of the ordinary.

-ABC News' Devin Dwyer

At a press conference, a Maricopa County official debunked misinformation circulating on X about voting centers in the county being shut down due to issues with the printers.

"There have been no vote centers that have been shut down," said Maricopa County Supervisor Bill Gates.

Earlier today, Tyler Bowyer, an executive with Turning Point USA who was charged in the Arizona 2020 fake elector case, posted on X that the right-wing group was sending buses to move people to functioning voting centers in Maricopa County.

"We have reports of multiple vote centers with ink issues in Maricopa County," Bowyer posted.

Gates said the printers are being serviced as usual. "We are out there going ahead and servicing the printers as we normally would," the Maricopa County official said in response to Bowyer's tweets.

The Maricopa County supervisor said that as of Monday, more than 1.5 million voters in the county had returned early ballots. About 70- 75% of those votes will be reported in the first batch of results at 8 p.m., he said.

Gates also said that if voters get in line at 7 p.m., they will have an opportunity to vote no matter how long lines are.

"Stay in line and go ahead and vote," he said.

-ABC News' Laura Romero

The FBI arrested a man in Michigan who allegedly posted threats online saying he would carry out a mass shooting on conservative Christians in the event former President Donald Trump wins the 2024 election, according to newly unsealed charging documents.

Isaac Sissel was taken into custody yesterday in Canton, Michigan, just two days after law enforcement reviewed his online posting.

The criminal complaint says Reddit had previously reported Sissel to the FBI in late September over various accounts he had with threatening usernames, including, "ShootUpTrulyRally" "WillShootTrumpSoon," "PlannigToShootTrump" and "PlanningToKillTrump."

Law enforcement contacted Sissel yesterday at a Travelodge hotel in Canton and found no weapons in a consented search of his room, though the affidavit notes "this was not surprising given that SISSEL stated [in his online post] that he 'hid the gun.'"

Sissel further told agents Trump "was a threat...that should have been assassinated, and that everything would be better if Trump was dead," the affidavit says. While he said he wouldn't personally assassinate Trump, he told agents he believed there would be violence during the election "and wouldn't rule out joining Antifa to protest."

Sissel, according to the affidavit, is a transient who has more recently lived around the University of Michigan campus and has several open warrants for his arrest on charges of stalking, harassment and harassing communications.

The arrest underscores the FBI's aggressive response to counter a wave of violent threats surrounding the presidential election, particularly in the wake of the two assassination attempts targeting Trump. In the affidavit, the FBI specifically noted Trump's plans to appear in Michigan for a rally late Monday.

According to his court docket, Sissel has not been arraigned and has not entered a plea to the charge as of Tuesday afternoon. He has not yet been assigned an attorney.

-ABC News' Alexander Mallin