(CNN)It sounds like a scenario from another era.
Millions of paper immigration files are stored in a sprawling network of limestone caves around Kansas City. Some of those underground storage facilities operated with reduced staffing during much of the pandemic.
And now, a group of people are suing the government, arguing their citizenship applications are still stuck in limbo due to an "unreasonable delay" in getting their records out of the caves and into the hands of immigration officials.
"It does seem somewhat mind-boggling and shocking that we're still dealing with paper, but we are," says Leslie Dellon, a senior attorney at the American Immigration Council who's representing the 13 people who recently filed a lawsuit over their naturalization applications. "It's just very frustrating for these people, whose lives are on hold, and it's just dragging on and on."
The case highlights how difficult the US immigration system can be to navigate, with layers of bureaucracy and a reliance on paper files that officials have acknowledged slows processing and deepened backlogs during the pandemic.
A complaint filed in federal court says all 13 plaintiffs are stuck "in a stress-filled limbo" and still waiting for US Citizenship and Immigration Services to schedule them for citizenship interviews more than two years after they applied. If their immigration history records, known as A-files, aren't retrieved and their interviews aren't scheduled soon, Dellon says, they could lose the chance to take their citizenship oaths and register to vote in time to participate in the upcoming midterm elections.
"They want to be able to vote in November, and the window's closing," Dellon says. "We felt this is the time to take action and to file suit and to get the government to prioritize these applications and get these people scheduled for interviews."
Dellon says it's likely the continued delays are affecting additional people as well. Her organization has heard from many others since announcing the lawsuit late last month, she says, and is considering whether to add them to the case.
Agencies say the backlog is shrinking and they've made major progress
The lawsuit comes months after a Wall Street Journal report detailed a backlog in citizenship application processing due to pandemic operating restrictions that reduced staffing at Federal Records Centers (FRC) run by the National Archives and Records Administration. At that time, the Journal reported there were 350,000 requests pending for immigration files held at the centers, located in underground caves around Kansas City, Missouri.
Now, officials say that backlog is down to about 40,000 pending requests concentrated at centers in Kansas City and Lee's Summit. Both locations are on track to eliminate the backlog by the end of July, the National Archives said.
The National Archives and USCIS declined to comment on the lawsuit, citing their policies of not commenting on ongoing litigation. But both agencies said in statements to CNN that they'd made significant progress in addressing the delays.
"Now that we have returned to full staffing, we have effectively made all remaining requests a priority and are on the verge of eliminating the backlog," the National Archives said.
USCIS has conducted initial processing on naturalization applications while it waits to receive the A-files, the agency said, to allow for quick completion once it gets the documents. And most of the applications would be near the front of the line for interviews and adjudication because they've been pending beyond normal processing times, USCIS said.
Earlier this year, the situation drew concern from Massachusetts' congressional delegation, which sent a letter to the National Archives in February.
"Our constituents have already been waiting many years for the opportunity to be eligible to naturalize," the lawmakers wrote. "It is truly unfortunate — and unacceptable — that many are now forced to wait significantly longer simply based on where their A-file is located."
Using the records centers for storage allows government agencies to meet requirements in a cost-effective manner, the Archives' statement said, noting that USCIS stores more than 2 million cubic feet of A-files there.
"Digitizing these records is currently cost prohibitive," the statement said.
Why these caves are used for storage
Limestone caves in the Kansas City area have been used to store immigration records for years.
USCIS opened its National Records Center in a cave in Lee's Summit, Missouri, in 1999. As the facility celebrated its 15th anniversary in 2014, officials said they had more than 20 million files in storage there and add 1.5 million new files every year.
The Archives' records centers located in limestone caves nearby house more than 50 million A-files transferred there by USCIS, including more than 1 million A-files of immigrants who were born more than 100 years ago and more recent records.
The caves are the result of extensive mining of limestone that was used for paving and building materials in the late 19th and early 20th century.
According to the Archives' historian, the caves were largely abandoned after a building boom in the area ended, and businesses started using the caves for storage in the 1950s. The Archives opened their first FRC in a mine in 1997, historian Jessie Kratz wrote in a 2016 article.
"Because the temperature is naturally around 60 to 70 degrees, there is significant savings in temperature and humidity control," Kratz wrote. "And underground storage is also less expensive than above-ground storage, with plenty of room for expansion and enhanced security."
The Kansas City FRC, one of the facilities that stores immigration records, is located in a vast underground business complex known as SubTropolis. The complex boasts more than 7.3 million square feet of industrial space for lease, and more than 6.7 million square feet available to grow into -- far larger than the country's biggest malls and stadiums, and on par with some of the world's largest buildings.
Its caves also house auto suppliers, data servers, food distributors, a pharmaceutical company and even a paintball and laser tag course.
He's afraid to leave the country while his case is pending
The Biden administration has said it's committed to making the naturalization process "welcoming and accessible to all who are eligible."
But the lawsuit argues delays have left applicants feeling frustrated and uncertain.
Some plaintiffs say they're scared their families could end up getting separated and afraid to travel out of the country while their cases are pending.
Ali Mohammed, 28, told CNN he hasn't returned to Iraq, even though his parents still live there and have had health problems. Without the guarantee of citizenship, he says, he's worried he could be blocked from returning to the United States by a sudden policy change, like travel restrictions that were put into place during the Trump administration.
"It's very concerning to me ... I don't want to risk it," he says.
Mohammed, a Kurdish refugee, came to the United States in 2015. He applied to become a citizen in April 2020, as soon as he was eligible, eager to vote in elections and improve his professional prospects.
Since then, other people he knows have applied and already become citizens, he says. The lawsuit notes that when a congressman asked about