On Tuesday night, police forces and the IDF's Efraim Division raided a home in Samaria-region Arab town of Kafr Biddya.
During their search, the forces found a homemade "Carlo" submachine gun, and took a local resident for questioning.
"Israel Police continue their determined efforts to locate and confiscate illegal weapons," a police spokesman said. "These weapons are often used to carry out terror attacks, commit crimes, and for violent incidents."
"Therefore, Israel Police and security forces will continue the determined and unrelenting battle, and work untiringly with the relevant authorities to reduce the numbers of illegally-owned weapons and protect all lsraeli citizens, allowing them to lead their lives in a normal and safe fashion."
In both April and August, Israel discovered illegal weapons factories in Palestinian Authority-controlled towns. One of the factory's owners may have held a permit allowing him to enter and exit pre-1967 Israel.