Thousands of people complained about votes in battleground states

`There is some problem between the post office and the sorting facility in Pittsburgh. We are not sure what the problem is,` Aaron Sheasley, director of elections in Butler County in Pennsylvania told CNN on October 30.

Mail ballots are sorted in West Chester, Pennsylvania on October 23.

To vote by mail, voters must first register.

After filling out all information in the ballot, the voter will put the ballot in a sealed envelope, then put it in a second envelope and sign for confirmation on the outside.

Butler County has about 150,000 registered voters.

Meanwhile, Marti Johnson, a US postal service spokeswoman, said they were not aware of any problems.

However, Sheasley said an investigation has shown that many ballots that were scheduled to be mailed on October 12 have not reached voters.

The problem in Pennsylvania is of concern because this is a battleground state with 20 electoral votes that have a major impact on the race to the White House.