A resident of the Arab town of Kafr Kanna in the Galilee was arrested on Sunday after Border Police found a gun, Palestinian flags, and military uniforms in his home.
Israeli security forces obtained a search warrant for the 51-year-old man's apartment after receiving a tip that he was in possession of illegal weapons.
During the search, police found a shotgun that they suspected was being converted into a pistol, as well as several Palestinian flags and military uniforms.
The suspect was taken in for questioning, and the court extended his detention until Wednesday.
Police open investigation into Jaffa shooting involving M16 rifle
Israel Police opened an investigation into a shooting in Jaffa that targeted a 33-year-old man on Monday night, the police said on Tuesday morning.
After conducting searches at the scene of the incident, police officers located an M16 rifle and a magazine filled with ammunition, seizing them both.
The man was seriously wounded in the incident and was evacuated to the hospital for medical treatment, the police said.
Initial police investigations indicate that the incident was criminal in nature.
The full circumstances are under investigation, the police stated.
James Genn contributed to this report.