60 needles have been found at a family-friendly park in Noarlunga Downs.
The used and unused syringes were strewn along a 50m stretch of the Perry's Bend Reserve in wetlands of the Onkaparinga River Recreation Park last weekend.
Volunteers for local environment group Our Coast, Our Mission will ramp up cleaning efforts from this weekend.
Authorities say it's unusual to see so many syringes in the one spot, assuming it's drug related and that they'd been dumped.
Anyone that spots suspicious activity in the area is urged to contact Police.