(AP) — As police departments around the country report a surge in 3D-printed firearms turning up at crime scenes, gun safety advocates and law enforcement officials are warning that a new generation of untraceable weapons could soon eclipse the “ghost guns” that have already flooded U.S. streets.

At a summit in New York City on Thursday, the advocacy group Everytown for Gun Safety will bring together policymakers, academics, 3D-printing industry leaders and law enforcement officials to confront the growing challenge. They fear that as the printers become cheaper and more sophisticated — and blueprints for gun parts spread rapidly online — the U.S. could be on the brink of another wave of unregulated, homemade weapons that evade serial-number tracking and background checks.

Numbers collected by Everytown from about two dozen police departments show how quickly the problem is growing: A little over 30 3D-printed guns were recovered in 2020. By 2024, that figure had climbed above 300. While still a fraction of the tens of thousands of firearms seized each year by the nation’s nearly 18,000 police departments, the spike mirrors the early trajectory of ghost guns — build-it-yourself weapons assembled from kits that for years eluded federal regulation.

“We are now starting to see what kind of feels very familiar,” said Nick Suplina, senior vice president of law and policy at Everytown. “It’s now at a small number of recoveries in certain major cities, such that it’s doubling or tripling year over year. We’re seeing this very familiar rate of growth and that’s why we’re getting this group together to discuss how to stop it.”

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives imposed new rules in 2022 requiring serial numbers, background checks and age verification for ghost-gun kits, regulations upheld by the Supreme Court earlier this year. Lawsuits and state-level bans eventually pushed Polymer80, once the leading manufacturer of those kits, out of business in 2024.

But 3D-printed weapons present a thornier problem. They aren’t manufactured or sold through the firearms industry, and neither 3D-printer companies nor the cloud-based platforms that host gun blueprints fall under the ATF’s authority. That leaves much of the prevention work to voluntary action and new legislation.

In addition to seeking industry self regulations, the summit aims to bring together academics and policymakers to talk about possible legislative ways to address the issue such as creating statutes to criminalize manufacturing ghost guns or selling blueprints.