Port Lincoln and Tumby Bay police are investigating the theft of two firearms that were stolen from a rural property between May 12 and June 4.
The firearms are described as a Squibman pump action shotgun and an Anschutz .22 bolt action rifle, and have yet to be located.
However, during the course of police investigations, two illegal firearms were found which are not connected to the theft.
A 20 year old man from Tumby Bay was arrested on June 5 in connection with the location of one of the illegal firearms and has been charged with possessing an unregistered firearm and possessing a firearm without holding a licence.
He has been bailed and will appear in the Port Lincoln Magistrates Court on July 9.
Police are still making enquiries into the second illegal firearm found.
SA Police have issued a reminder for those who lawfully possess firearms to maintain their security in compliance with firearms legislation at all times.
Any person with information in relation to the theft or the supply of any other illicit firearm is asked to call Crime Stoppers on 1800 333 000.