More than 900 young immigrants applying for a renewal of temporary work permits had their applications rejected because of mail problems, a number far greater than immigration lawyers had thought.

The U.S. Citizenship and Immigration Services acknowledged the significant impact today, as it released information on how those who had been turned down could submit new applications.

The immigrants were trying to renew their work permits under the program known as Deferred Action for Childhood Arrivals, or DACA, which allowed nearly 800,000 immigrants who were brought to the country illegally as children to work and go to school in the United States without fear of deportation.

On Sept. 5, the Trump administration canceled the program, but said those whose permits were expiring before March 5, 2018, could renew their application by Oct. 5 for a two-year period.

Citizenship and Immigration Services said it was in the process of sending letters to 900 people it had identified whose applications had arrived at the post office on time but not been officially received by the agency until after the deadline. Once applicants receive that letter they will have 33 days to resubmit their applications, the immigration agency said.

The agency said there could be more people affected and that it was working with the U.S. Postal Service to determine how many applications were delayed by problems there. At least 4,000 renewals were rejected because they were late, according to a government official in an Oct. 18 deposition in a federal lawsuit over the cancellation of DACA.

The information USCIS released today still left questions unanswered; the agency said it would soon provide “specific guidance” on the steps DACA recipients must take to resubmit their renewal requests.

What the government did provide, however, was small comfort for some people whose DACA permits have expired or are expiring soon, and lawyers questioned the government’s lack of expediency.

The government said those DACA recipients would not be able to work until their permit is officially renewed. But, the agency added, they would not be a priority for deportation.

“We’ve lost two months now,” said Hasan Shafiqullah, director of the immigration unit of the Legal Aid Society in New York. That immediately affected one of his clients, whose DACA permit expires Friday.

“What will USCIS do to mitigate that harm and cost to her?” he asked. “The least they can do is expedite the adjudication of the renewal, so she can get her work permit as fast as possible.”

USCIS said applicants who believed their renewal had been rejected because of mail problems could contact someone in the support department, via email. But that does not appear to promise quicker action.

Shafiqullah said he emailed the agency Nov. 8 and, 22 days later received an email response that began: “Thank you for contacting Lockbox Support and I apologize for the delay in our response to your inquiry.”

There are three Citizenship and Immigration Services locations, known as lockboxes, where agency mail is delivered: in Phoenix, Chicago and Lewisville, Texas, a suburb of Dallas. All three were affected by mail problems, according to immigration activists, but Chicago had the most applications delayed.

Three weeks ago, lawyers and lawmakers said they initially knew of 74 people in New York and Chicago whose renewals were delayed by mail problems. The U.S. Postal Service took the blame, but at the time, the immigration agency remained firm in its policy: It would still reject those applications.

A week later, the agency reversed its policy, allowing people to reapply with proof of a delay. By that point, lawyers and lawmakers had reported 115 cases in Texas, Wisconsin, Washington state, North Carolina and Michigan.

Today, USCIS said approximately 450 applications had been delayed in the mail in Texas, 390 in Chicago and 60 in Phoenix.

Immigration advocates said the government opened itself to problems by providing a short window for renewal after the Trump administration said it was ending DACA. They gave those eligible to apply for renewals just one month to get their applications in. And, departing from typical immigration application guidelines, the DACA renewals had to be received by the immigration agency by the Oct. 5 deadline, not postmarked.

Many applicants sent their applications in three weeks in advance — by certified mail — and were still caught in the mail delays. Lawyers do not intend to take any chances this time. “We’re doing FedEx,” Shafiqullah said.