Updated

The United States Postal Service failed to meet a deadline to conduct a sweep of its facilities in dozens of districts around the country for undelivered mail-in ballots and to deliver them last-minute on Election Day.

Earlier Tuesday, U.S. District Court Judge Emmet Sullivan ordered the U.S. Postal Service to conduct a sweep of its facilities between 12:30 p.m. and 3 p.m. 

"Given the time constraints set by this Court's order, and the fact that Postal Inspectors operate on a nationwide basis, Defendants were unable to accelerate the daily review process to run from 12:30 p.m. to 3:00 p.m. without significantly delaying preexisting activities on the day of the election," the USPS wrote in a release. 

The USPS said that some 300,000 ballots lacked a delivery scan. 

"There are only one or two Inspectors in any one facility, and thus they do not have the ability to personally scour the entire facility. Indeed, doing so would be impractical (given the size of that facility) and would take them away from their other pressing Election Mail-related responsibilities, as detailed above," the USPS continued. 

The Postal Service said that inspectors will be in the identified facilities "throughout the evening," though dozens of states will reject ballots not received tonight. 

Tuesday is the final day by which ballots can be postmarked in order to be counted in the 2020 election, and even states that are accepting ballots beyond Election Day have hard deadlines before ballots will be turned away.

FEDERAL JUDGE ORDERS USPS TO TAKE 'EXTRAORDINARY MEASURES' TO DELIVER MAIL-IN BALLOTS ON TIME

"[B]eginning no later than 12:30 PM EST today, Defendants shall send Postal Service inspectors or their designees, to processing facilities in the following Districts and direct them to sweep the facilities between 12:30 PM EST and 3:00 PM EST to ensure that no ballots have been held up and that any identified ballots are immediately sent out for delivery," Sullivan ordered. Alternatively, Sullivan said the USPS Inspector General's Office can send investigators.

Those districts are: Central Pennsylvania, Philadelphia, Detroit, Colorado/Wyoming, Atlanta, Houston, Alabama, Northern New England, Greater South Carolina, South Florida, Lakeland (covering parts of Illinois and Wisconsin) and Arizona.

DEPLOYED US MILITARY MEMBERS EXPRESS CONCERNS OVER MAIL-IN BALLOT COUNT

The districts were determined based on those that had low scores when it comes to processing mailed ballots.

After the USPS finishes the sweeps, they must submit a status update to the court no later than 4:30 p.m. ET.

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Tuesday's order follows an Oct. 28 ruling in which Sullivan ordered the USPS to rescind rules issued in the summer that limited late and extra delivery trips.

Sullivan said in that order that the USPS must notify staff that guidelines from July 14 no longer apply and that "personnel are instructed to perform late and extra trips to the maximum extent necessary" at the same or a greater rate than before those guidelines were issued, in order to increase timely mail delivery, especially election mail.

Fox News' David Spunt contributed to this report.