Yallingup surf spot, Three Bears, will remain closed until Monday, May 14.
The Department of Biodiversity, Conservation and Attractions extended its Regulation 44 closure due to the whale carcass south of the surfing spot.
The whale carcass has dislodged, and was sighted one kilometre offshore on May 9.
However, an inspection of the original site suggested some parts of the whale carcass remain and several large sharks have been reported in the area.
The closure is from Three Bears surfing spot to 300 metre north of Shivery Rock surf break.
A further assessment will be carried out, before the closure ends next Monday.
Shark sightings should be reported to Water Police on 9442 8600.
To find the latest detection and sighting information, visit sharksmart.com.au/shark-activity or the Surf Life Saving WA Twitter – twitter.com/SLSWA.