The world's first gun made with 3D printer technology has been successfully fired in the US.
The controversial group which created the firearm, Defense Distributed, plans to make the blueprints available online.
The group has spent a year trying to create the firearm, which was successfully tested on Saturday at a firing range south of Austin, Texas.
Anti-gun campaigners have criticised the project.
Europe's law enforcement agency said it was monitoring developments.
Victoria Baines, from Europol's cybercrime centre, said that at present criminals were more likely to pursue traditional routes to obtain firearms.
She added, however: "But as time goes on and as this technology becomes more user friendly and more cost effective, it is possible that some of these risks will emerge."
Defense Distributed is headed by Cody Wilson, a 25-year-old law student at the University of Texas.
Mr Wilson said: "I think a lot of people weren't expecting that this could be done."
To make the gun, Mr Wilson received a manufacturing and seller's licence from the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
Donna Sellers, from the ATF, told BBC News that the 3D-printed gun, as long as it was not a National Firearms Act weapon (an automatic gun, for example), was legal in the US.
She said: "[In the US] a person can manufacture a firearm for their own use. However, if they engage in the business of manufacture to sell a gun, they need a licence."
Amid America's ongoing gun debate in the wake of the shootings at Sandy Hook Elementary School in Newtown, Connecticut, US congressman Steve Israel recently called for a ban on 3D guns under the Undetectable Firearms Act.
Groups looking to tighten US gun laws have also expressed concern.
Leah Gunn Barrett, from New Yorkers Against Gun Violence, has said: "These guns could fall into the hands of people who should not have guns - criminals, people who are seriously mentally ill, people who are convicted of domestic violence, even children."
3D printing technology has already been used by some criminal organisations to create card readers - "skimmers" - that are inserted into bank machines.
Many law enforcement agencies around the world now have people dedicated to monitoring cybercrime and emerging technologies such as 3D printers.
Ms Baines from Europol said: "What we know is that technology proceeds much more quickly than we expect it to. So by getting one step ahead of the technological developments, we hope and believe we will be able to get one step ahead of the criminals as well."