Story highlights UK police raid model-shop looking for 3-D printed gun

The parts they found may actually be replacement pieces for the 3-D printer itself

3-D printed firearms a growing concern for law enforcement since first one fired in May

Sometimes a 3-D printer part is just a 3-D printer part.

Police thought they had seized the UKs first 3-D-printed gun on Thursday when they raided a local model-making shop, arrested its 38-year-old owner, and confiscated a 3-D printer and a number of parts they believed were for a 3-D printed gun.

However, it now appears the parts are likely just replacement components for the 3-D printer itself.

Officers suspected one piece was a 3-D-printed plastic magazine and the other a 3-D-printed trigger. The seizure was part of a larger raid targeting organized crime by the Greater Manchester Police.

"If what we have seized today can, as we suspect, be used to make a genuine firearm then today will be an important milestone in the fight against this next generation of homemade weapons," said detective inspector Chris Mossop in a statement announcing the raid.

Photos of the parts were quickly picked apart online by the 3-D printing community, including GigaOm , and identified as pieces for a 3-D printer. The store owner told the BBC the "magazine" part was actually a "spool holder" for the printer, and that the parts were designed by the printer manufacturer.

In a follow-up statement , the department acknowledged that they could not confirm the parts were from a 3-D printed gun, saying they needed further forensic testing by ballistics experts. They also plan on searching through the shop-owner's computer for any incriminating files that might indicate he planned on printing a 3-D weapon.

In addition to the plastic components, officers found air rifles and an air pistol in the shop, and said they had "intelligence about the possible production of a weapon using this technology."

These particular parts may not be for a gun, but law enforcement officials feel the threat of homemade firearms is very real.

Since the first 3-D printed gun was successfully fired in May, 3-D printing technology has been on police radars. The printers are dropping in prices, costing anywhere between $300 and thousands for a home 3-D printing machine.

Before they were taken down, the blueprint files needed to make a gun were available online for anyone to download.

"What this has also done is open up a wider debate about the emerging threat these next generation of weapons might pose," assistant chief constable Steve Heywood said in a statement.

"The worrying thing is for me is that these printers can be used to make certain components of guns, while others can be legitimately ordered over the Internet without arousing suspicion. When put together, this could allow a person to construct a firearm in their own home."

The 3-D printed gun technology is still in the early stages, but if it irons out the kinks and makes it affordable and easy to produce guns at home, it would create new opportunities for criminals hoping to stay off the radar.