The paperwork was mailed from New York in plenty of time. On Sept. 14, Allison Baker, a lawyer for the Legal Aid Society, sent a client's application to renew a permit that would let him stay and work in the United States legally as part of the Deferred Action for Childhood Arrivals program — long before the Oct. 5 deadline. It was sent certified mail to be safe.

Tracking data from the U.S. Postal Service shows the envelope arriving in Chicago on Sept. 16 on its way to the regional processing warehouse of the U.S. Citizenship and Immigration Services, the agency that administers the program known as DACA.

Then the packet started circling Chicago in a mysterious holding pattern. From Sept. 17 to 19, it was "in transit to destination." Then its tracking whereabouts disappeared until Oct. 4. Once again, it was "on its way."

On Oct. 6, a day too late, it was delivered. The application, for a 24-year-old man who asked to be identified as José because his legal status was uncertain, was rejected.

In at least 33 other cases, unusually long Postal Service delays resulted in rejections of DACA applications, throwing the lives of their clients into frantic limbo. Lawyers in Boston and Philadelphia, which also send applications to the Chicago processing center, said they have not seen an issue with the mail.

But in Chicago, in the backyard of the U.S. Citizenship and Immigration Services agency, there were at least 41 DACA recipients whose renewals, sent well before the deadline, arrived late. An applicant sent a renewal Sept. 13 and it arrived Oct. 6. Another sent the paperwork Sept. 21; it was received Oct. 9.

"Because somebody else did not do their job correctly, we are taking innocent young immigrants and making them deportable," said Rep. Luis Gutiérrez, D-Ill. "That is unacceptable."

On Thursday, in a rare admission from a federal agency, the U.S. Postal Service took the blame. David Partenheimer, a spokesman for the post office, said there had been an "unintentional temporary mail processing delay in the Chicago area."

But the U.S. Citizenship and Immigration Services agency said nothing more could be done; the decisions were final.

"According to USCIS regulations, a request is considered received by USCIS as of the actual date of receipt at the location for filing such request," Steve Blando, a spokesman for the agency, wrote in a statement. He added: "USCIS is not responsible for the mail service an individual chooses, or for delays on the part of mail service providers."

He later added, though, that "USCIS is committed to working with the USPS to understand and address the USPS error that occurred that delayed the mail."

Because DACA is an executive order, signed by President Barack Obama in 2012, and not a statute, applicants cannot appeal. Still, immigrants and their advocates viewed the agency's unwillingness to revisit their applications as harsh and unfair.

"You can't put the burden on the applicant to ensure the government agencies did their job," said Camille Mackler, director of legal initiatives for the New York Immigration Coalition. "Can you imagine if the IRS didn't pick up their mail for two weeks and you get a penalty because of it?"

The DACA program had offered temporary protection and work permits for about 800,000 young adults who had been brought to the U.S. illegally as children.

On Sept. 5, Attorney General Jeff Sessions announced after months of speculation that the Trump administration was canceling the program. Recipients were allowed to keep their permits until they expired at the end of the current two-year term. The administration also offered a brief renewal window for recipients whose permits were expiring before March 5, which set off a scramble across the country from legal service providers to assist applicants.

There are three U.S. Citizenship and Immigration Services intake locations, known as lockboxes, in the U.S.: in Phoenix, Chicago and Lewisville, Texas, a suburb of Dallas.

According to the immigration agency, its employees do not pick up the mail from the lockbox. The U.S. Department of the Treasury manages the process, but uses a courier service that picks up the mail from post offices each morning. Express Mail items, the agency said, are picked up in the afternoon. Also, items are delivered to the lockbox by FedEx, DHL and the United Parcel Service.

In a memo after DACA was rescinded, the Department of Homeland Security said renewals had to be "accepted" by Oct. 5. Immigration lawyers contrasted that with a permanent residency opportunity the government offered in 2001, when applications only had to be postmarked by the deadline of April 30. The government offered a grace period with a May 3 deadline.

According to an Oct. 18 deposition of an immigration official conducted as part of a lawsuit, 4,000 DACA applications arrived late. One hundred and fifty-four thousand people were eligible to apply for renewal and 132,000 applications arrived on time.