U.S. Postal Service records show delivery delays have persisted across the country as millions of Americans are voting by mail, raising the possibility of ballots being rejected because they arrive too late.

Postal data through Oct. 9, the latest numbers available, show nearly all the agency’s delivery regions missing its target of having at least 95% of first-class mail arrive within five days. Parts of the presidential battleground states of Minnesota, Wisconsin, Michigan, Pennsylvania and Ohio fell short of delivery goals by wide margins as the agency struggles to regain its footing after a tumultuous summer.

The districts that included the major urban areas and their suburbs in each of those states all performed below the national average for on-time delivery, with the area around Pittsburgh in western Pennsylvania the lone exception.

The delays are a worrisome sign for voters who still have not returned their absentee ballots. That is especially true in states such as Michigan, where ballots must be received by Election Day. Other states require a postmark by Nov. 3.

“We do encourage people who are worried about ballots not getting here on time to get them in as soon as possible,” said Perry County Commissioner Brenda Watson in Pennsylvania.

She said her office has sent out more than 600,000 absentee ballots, more than double the number from the primary, and has extended office hours so staff can monitor a drop box.

With more than 2.9 million mail-in ballots requested in Pennsylvania, on-time delivery is crucial. But delays are lingering throughout the state, according to postal data released as part of a federal court order.

In the week that ended Oct. 9, first-class mail was delivered on time 79.7% of the time in the district covering Philadelphia and its suburbs, and 83.2% of the time in central Pennsylvania, both below the national average of 86.1%.

A deadlock at the U.S. Supreme Court this week allowed the state to count mailed-in ballots received up to three days after the Nov. 3 election, although Republicans have filed another challenge.

Delays have plagued the Postal Service during the coronavirus pandemic and worsened under a series of cost-cutting policies implemented by Postmaster General Louis DeJoy, who took over the agency in June. Following a series of court orders and intense public scrutiny, the agency has reversed the policies and seen improvements, but has not yet fully restored delivery times.

“As these delays continue across the country just weeks before the upcoming presidential election, it is incumbent upon you to take immediate and necessary actions to fully restore on-time mail delivery,” U.S. Sen. Gary Peters, a Michigan Democrat, wrote to DeJoy this week.