WASHINGTON — Election Day unfolded relatively smoothly as voters across the country faced only scattered disruptions and delays despite concerns about disinformation, foreign influence, and threats to election workers and voting systems.

A series of bomb threats turned out to be hoaxes in parts of Georgia and Arizona, two presidential battleground states, and federal officials warned that Russia was seeking to sow chaos and uncertainty into America’s vote for president. And despite no evidence of widespread problems, former President Donald Trump made unsubstantiated claims related to Philadelphia and Detroit, the biggest cities in two states that will be crucial for deciding the presidency.

Local officials quickly knocked down the claims Trump made on his social media platform, saying they had seen nothing amiss.

It was expected that at least half of all votes to be cast had already come in by Tuesday, with more than 84 million Americans voting early. There were just a few hiccups and frustrations during early voting in the presidential battlegrounds of Pennsylvania and Michigan.

The problems that cropped up on the final day of voting were “largely expected, routine and planned-for events,” said Cait Conley, senior adviser to the director of the Cybersecurity and Infrastructure Security Agency. The agency was not seeing any significant national incidents affecting election security, she said.

In Milwaukee, election officials said they were recounting more than 30,000 mail ballots “out of an abundance of caution” after it was discovered that doors on the back of ballot scanners were not properly sealed. The effort, which drew the attention of Trump and the Republican National Committee, was expected to delay the count there.

Voters also faced some more typical election mishaps. In Arizona’s Maricopa County, one voting location was slightly delayed when a worker forgot to bring a key. In Pennsylvania’s Allegheny County, an election judge failed to show up at the polls.

Some voters were delayed around the country because of problems checking-in at polling stations. Ballot printing mistakes in some areas required voting hours to be extended. And extreme weather across the country’s midsection caused flooding and isolated power outages, including one that forced a polling station to use a generator to keep voting up and running.

In western Pennsylvania, a few counties reported problems with machines that scan and count paper ballots. A Pennsylvania state judge ordered polls to remain open for two extra hours in Cambria County, which voted 68% for former President Donald Trump in 2020. The county sought the extension after a software malfunction affected the ballot-scanning machines, but officials said no one was turned away from the polls and all ballots would be counted. It was not yet clear how the extension might affect vote-counting timelines.

Bomb threats mobilized law enforcement in Arizona and Georgia. They were reported at various times throughout the day in three metro Atlanta counties, all with large numbers of Democratic voters. About a dozen polling places in all three counties stayed open late. Bomb threats also were reported at three voting locations in Navajo County, Arizona, according to the secretary of state’s office.

The FBI on Tuesday afternoon said it was aware of multiple hoax bomb threats to polling locations in several states and said many of them appeared to originate from Russian email domains.

The massive early voting turnout before Tuesday — slightly more than half the total number of votes in the presidential election four years earlier — was driven partly by Republican voters.