In a court filing early Friday, USPS said 1,076 ballots, had been found at the USPS Philadelphia Processing and Distribution Center. About 300 were found at the Pittsburgh processing center, 266 at a Lehigh Valley facility and others found at other Pennsylvania processing centers.
In court, a Justice Department lawyer said it appears 668 of the 1,076 ballots in Philadephia were discovered on Wednesday and not Thursday.
Ballots must be received by Friday evening in Pennsylvania in order to be counted. The vote for the U.S. president remains extremely close and Pennsylvania is one of the states that remains undecided.
There are about 15 states that have ballot receipt deadlines next week.
About 500 ballots were also discovered in North Carolina during sweeps, USPS said on Friday.
U.S. District Judge Emmet Sullivan on Thursday had ordered twice-daily sweeps at USPS facilities serving states with extended ballot receipt deadlines as votes were still being counted in U.S. election battleground states.
Sullivan plans to hold another status conference on Monday.
Some states, including Nevada and North Carolina, are counting ballots that are received after Election Day as long as they were postmarked by Tuesday.
A lawyer for Vote Forward, Shankar Duraiswamy, said at court hearings this week that USPS delivered about 150,000 ballots on Wednesday and 40,000 on Thursday.
"The vast majority were destined for postmark states and would be delivered on-time under state election law," USPS said Thursday.
Sullivan said processing centers must perform morning and afternoon sweeps "to ensure that any identified local ballots can be delivered that day."
Ballots were still being counted by election officials in battleground states after polls closed Tuesday in one of the most unusual elections in U.S. history because of the novel coronavirus pandemic.
Democratic candidate Joe Biden has taken narrow leads over Republican President Donald Trump's in Pennsylvania and Georgia. The former vice president also retains slim margins in Nevada and Arizona.
