The BBC has reported that a 3D printer and suspected "homemade" gun components have been seized during police raids in a town near Manchester.
A plastic magazine and trigger, which police suspect could be fitted together to make a firearm, were found in Wythenshawe on Thursday.
Greater Manchester Police said forensic experts were assessing whether the parts could make a genuine gun.
A man has been arrested on suspicion of making gunpowder and remains in custody.
A force spokesman said if the tests showed the parts could make a functioning weapon, it would be the "first ever seizure of this kind in the UK".
A 3D gun featured on our top 5 list of 3D-printed objects.