COLUMBUS (WCMH) — With homicides on the rise in Columbus and other U.S. cities, a major step in the crime-solving process is taking longer than ever before.

One of the most powerful clues in solving a gun crime is knowing where that gun came from, with help from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives’ National Tracing Center.

NBC4 Investigates visited the tracing center and found a backlog that’s causing delays in the tracing process nationwide.

Every gun recovered by law enforcement nationwide gets traced at the same facility, the ATF’s National Services Center in Martinsburg, West Virginia.

The facility that is overflowing with growing piles of paper records, while tracing requests pour in in record numbers.

“It’s not just punching the (gun’s) serial number in,” said ATF Program Manager Neil Troppman. “We are piecing together the chain of distribution of that gun from start to finish.”

Federal law prohibits the creation of a national database of gun owners, Troppman said. Therefore, tracing a firearm is a manual, tedious, and sometimes time-consuming process.

The Gun Control Act of 1968 requires every licensed firearm dealer to keep a record of each sale, so every trace starts with a phone call, either to the gun’s U.S. based manufacturer or licensed importer.

“(We) basically ask them what they did with the firearm,” Troppman said.

The tracer follows the chain of transactions until they discover the first unlicensed purchaser, which is often a valuable lead for local law enforcement investigators.

If a retailer goes out of business, they are required to ship the records to the ATF.

According to Troppman, the National Services Center receives between 6 million and 8 million firearm sale records per month, which outpaces the rate at which the documents can be scanned into a digital format before the paper record is destroyed.

As a result, the center is packed with thousands upon thousands of boxes, full of sale records.

Making matters more complicated, Troppman said there is no uniform method of recording firearm sales.

“We’ve gotten these records in all kinds of different formats,” Troppman said. “Literally just scribbled on napkins or pieces of paper.”

Records sometimes arrive wet or damaged after a fire or natural disaster, making them difficult or impossible to read.

The boxes are now spilling into the parking lot, filling more than 35 shipping containers.

Troppman said the first two containers arrived roughly 12 years ago amid concern that the weight of the boxes would cause the floor inside the building to cave in. (The floor has since been reinforced, “but that didn’t give us the green light to keep more boxes in here,” Troppman said.)

“We have far outgrown … our space here,” said Troppman.

When the ATF first occupied the Martinsburg building around the turn of the millennium, it received roughly 150,000 to 200,000 trace requests per year, according to Troppman.

“Last year we received over 490,000 trace requests, and this year we’re on pace to receive over 540,000 trace requests from law enforcement,” he said. “This is just a point where we’re dealing with the highest volume of work we’ve ever seen.

That, plus the backlog of records, has led to longer turnaround times for non-urgent trace requests, which once took as little as four days. Now, a request could take seven to 10 business days to complete.

“As far as we’re concerned right now, 10 days turnaround time — that’s too long,” Troppman said. “We’re going to get this turnaround time back down again.”

Troppman said the ATF is adding funding and resources, including more people to help with traces. The agency is also exploring ways that technology can help speed up the tracing process, without illegally creating a searchable database.

The ATF is also launching Crime Gun Intelligence Centers in partnership with local law enforcement across the country to help them solve crimes. The centers serve as a clearinghouse for tracing information, forensic evidence, and local intelligence.

The Columbus CGIC launched in June.