The US Postal Service (USPS) said about 1,700 ballots had been identified in Pennsylvania at processing facilities during two sweeps Thursday and were in the process of being delivered to election officials.
In a court filing early Friday, USPS said about 1,070 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.
Ballots must be received by Friday evening in Pennsylvania in order to be counted. The vote for the US president remains extremely close and Pennsylvania is one of the states that remains undecided.