On Tuesday police stopped two vehicles for a driver test, both drivers returned positive results to drugs.
A 29-year-old Port Lincoln man tested positive to cannabis and a 33-year-old Port Lincoln woman tested positive to methamphetamine.
Both drivers may face further chargers following forensic analysis.
On the same day police stopped a Holden sedan on Liverpool Street the driver, a 19-year-old Port Lincoln man, tested positive to methamphetamine.
The man was also arrested for carrying an offensive weapon and possession of prescription medication.
The passenger in the vehicle, a 27-year-old Port Lincoln man was also arrested for carrying an offensive weapon, after a knife was located hidden down the front of his jeans.
Both men were bailed to appear in court at a later date.