A sealed blue container weighing 200 kilograms washed ashore at Jongensfonteinstrand near Stilbaai on Friday.
The National Sea Rescue Institute (NSRI) says it contains dangerous chemicals and should not be handled by the public.
Spokesperson Craig Lambinon says the Garden Route Disaster Risk Management (GRDRM) team will remove the container on Saturday.
He says there are fears that a few more containers might be adrift at sea in the area and may wash ashore along the South Cape Coastline.
The NSRI says there have been no reports of any dangerous chemical containers missing off any ship at sea and its origin will be investigated.
Any bathers or public members who might spot such a container are urged to contact authorities immediately.
The GRDRM's number is 044 805 5071
