As millions of people cast their votes in the US election, claims questioning the integrity of the vote spread online.

Election officials quickly dismissed some allegations of misconduct in the election and clarified some legitimate issues that were taken out of context.

BBC Verify tracks and investigates the most shared claims – here are four.

An image on social media shows a person holding a mail-in ballot with Kamala Harris' name already written on it.

The person who posted it on X claims that voting for someone else would result in the ballot being invalidated.

One post, which has been viewed more than three million times, said the image showed “strange voting shenanigans.”

BBC Verify spoke to the Kentucky Board of Elections, which denied the claim.

So far, 130,000 ballots have been mailed and there have been no complaints about mail-in ballots with pre-printed markings in the candidate selection boxes.

“Because no one has submitted a preprinted ballot to election administrators or law enforcement, the allegation that at least one ballot in Kentucky may have had a preprinted ballot currently exists only in the vacuum of social media,” it said.

The elections board added that for mail-in ballots in Kentucky, if more than one candidate choice is marked in ink, the ballot will still be counted if the voter circles their preferred choice.

A post on X what claims “The Pentagon Reportedly Failed to Send Mail-in Ballots to Active-duty Military Members Ahead of the Election” has been viewed over 28 million times.

It refers to a letter to Secretary of Defense Lloyd Austin, written by three Republican congressmenand expressed “grave concern” about “deficiencies” in voting procedures for foreign military personnel.

However, the letter does not accuse the Pentagon of failing to send them mail-in ballots.

It's not the Pentagon's job to do this – military members can vote abroad the Federal Voting Assistance Program (FVAP) and ballots will be mailed to you by election officials if you are registered in the United States.

If there is a risk that the ballot will not arrive before the voting deadline, employees can vote via a so-called Federal Write-In Absentee Ballot (FWAB).

The letter alleges that an unspecified number of “soldiers” requested a FWAB but were told their base had been exhausted. However, it is possible to download and sign one the FVAP website.

We asked the Ministry of Defense for details about how many people were affected by the issue, but they declined to comment. However, it said it had trained 3,000 election support officers to assist staff in casting votes.

Officials in the US state of Pennsylvania have denied claims that “illegal voters” can request ballots and vote at an election office in Allegheny County.

They released a statement after posts on X went viralclaiming to show “illegal voters” being ushered past US voters waiting in line.

A video that appears to show someone repeatedly trying and failing to vote for Donald Trump on a voting machine in Laurel County, Kentucky – before a voice appears next to Kamala Harris' name – has gone viral.

The person who posted it says: “I pressed Trump's name 10 times and it didn't work. Then I started recording and you can see what happened…”Switched it to Harris.”

Another post, which has been viewed nearly seven million times, shows the video claiming: “Voting machines in Kentucky are literally changing the vote from Donald Trump to Kamala Harris. This is election interference!”

Election officials confirmed the video was authentic and the machine malfunctioned, but said it was an isolated incident and that the voter was able to cast their vote as intended.

“After trying to recreate the scenario for several minutes, it actually happened. This was achieved by hitting an area between the boxes. Afterward, we attempted to try again for several minutes but were unsuccessful,” the county clerk said in a statement.

The machine in question was taken out of service until it was inspected and verified by the county clerk later in the day posted a video on Facebook shows that the machine is working properly.

“There are always going to be some problems in an election of this magnitude,” said Joseph Greaney, an election expert at US election website Ballotpedia.

“It may be one or two machines, but people extrapolate these to larger problems, but I would say with a good degree of certainty that these are isolated incidents and that they are being detected,” he added.