The same 3D printers that can generate car parts and jewelry are also being used to create small plastic blocks that transform pistols into machine guns, federal prosecutors in Texas warned Monday as the Lone Star State became the latest to go after the deadly "switch" inserts.

U.S. attorneys announced "Operation Texas Kill Switch," a statewide operation to target machine gun conversion devices, also known as switches or auto-sears. The switches – which prosecutors said can be made within minutes using a standard 3D printer – have been used in shootings across several cities, including Houston, Sacramento and Washington D.C.

“We’re here to talk about a roughly one-inch piece of plastic. It looks innocuous enough, a little like a LEGO or a k’nex block. But this one-inch piece of plastic is killing people,” said Leigha Simonton, the U.S. attorney for the Northern District of Texas. “Machine gun conversion devices can turn Second Amendment-protected firearms into illegal weapons of war, and petty criminals into brutal killers. We cannot have our streets turned into war zones."

Local Crime Stopper programs in Texas are offering cash rewards until Aug. 31 for information that leads to the apprehension or prosecution of people who possess switches or 3D printers that are being used to manufacture them. Prosecutors also urged local law enforcement to partner with federal agents on switch cases.

A standard 3D printer can make about 100 plastic switches in 72 hours, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives. and a switch-equipped gun can fire shots faster than the standard M-4 machinegun issued to U.S. soldiers.

Federal agents have seen a spike in switches across the United States. ATF seized 5,454 machine gun converters between 2017 and 2021, up by 570% from between 2012 to 2016. In Texas alone, ATF agents seized nearly 1,000 switches between 2017 and 2023, and half of them were recovered just last year.

Federal gun agents said Monday that the switches are often sold over social media, marketed to adults and juveniles alike.

3D printers used across U.S. to make switches

3D printing is the process of building three-dimensional objects by layering materials using computer-aided design models, according to 3D printing company Formlabs. The technology has been around since the 1980s but recent advances have made the printers more affordable and accessible, allowing them to be used for industries such as healthcare, dentistry, jewelry and entertainment.

Kill switches can be made out of metal or plastic within minutes using a 3D printer, according to prosecutors. They usually slide into the butt of a gun and allow the shooter to fire dozens of rounds with the single pull of a trigger.

In Mississippi, a man was sentenced to 14 years in federal prison last year for converting semi-automatic weapons into machine guns using switches he made from 3D printers.

An Ohio man was sentenced to three years in prison for using a 3D-printed switch on his Glock. Federal prosecutors said he fired in self-defense but still broke the law by owning the switch. Except in very limited circumstances, possession of a switch is illegal, as the National Firearms Act classifies the switch itself as a machinegun, prosecutors said Monday.

In Indianapolis, a man admitted to selling switches he made using a 3D printer and was sentenced to seven years in prison.

“I have been in this business for a long time, and nothing scares me more than the rapid flood of machine gun conversion devices on the streets of Texas and beyond," said ATF Dallas Field Division Special Agent in Charge Jeffrey C. Boshek II. "Rest assured that ATF and its partners are doing everything we can to stop the flow of these things and to prevent the carnage they can create."

States try to combat surge in switches

Federal agents and state authorities are grappling with a spike in switches, which allow a shooter to fire several hundred rounds per minute, ATF spokesperson Kristina Mastropasqua told USA TODAY.

The National Firearms Act classifies the switch itself as a machine gun, and owning a conversion device carries a maximum penalty of 10 years in federal prison and $250,000 fine.

Some states are launching programs to eliminate switches.

Federal prosecutors in Oklahoma announced last week that a man was sentenced for possessing a machine gun conversion device as part of an initiative launched in November targeting switches. New York introduced a bill to ban the sale of "convertible pistols," or guns that can easily be transformed into a machine gun using a conversion kit. Maryland Gov. Wes Moore signed a bill last month that included a ban on switches.

And the city of Chicago sued Glock in March for manufacturing pistols that can easily be converted into machine guns using switches.

"This increasing demand for machineguns by criminal elements does not just present a public safety danger, it is unsafe for law enforcement, as well, who are increasingly outgunned by the weaponry they face," Mastropasqua said. "To be clear, making, selling, and just having a machine gun 'conversion device' is against the law."