Vale of Glamorgan Council is urging beachgoers to stay clear of the cliff area as assessments continue following the incident, which was reported on Monday afternoon.
Teams remain at the scene, inspecting the cliffs and monitoring for further risk.
Jackson’s Bay is one of eight designated bathing waters in the Vale and is routinely monitored throughout the bathing season by Natural Resources Wales and other partners.
The beach itself remains open to the public, but visitors are being reminded to take extra care near the cliff-backed sections of the shore.
Officials are relying on signage, on-site checks and public cooperation while the investigation continues.
Jackson’s Bay, like other parts of the Vale coast, is known for its unstable cliffs and history of periodic rockfalls.
A combination of coastal erosion and heavy rain has previously led to large boulders and debris falling onto the sand.
Beach safety guidance for the area warns against sitting beneath cliff faces and stresses that warning signs and barriers should be taken seriously.
Officials say rockfalls are unpredictable and can vary in size from small fragments to boulders “as large as a car”.
To minimise the risk of injury, visitors are urged to give cliff lines a wide berth at all times.
With warm weather expected and the bathing water season in full swing, the council is suggesting beachgoers consider other nearby locations while work continues at Jackson’s Bay.
Alternatives include Whitmore Bay, Watch House Bay, the Knap and other designated sites along the Barry and Llantwit Major coastline.
All are monitored for water quality and equipped with safety signage.
The council is also asking the public to report any further signs of rock movement to the authority or the coastguard.
Visitors are reminded to follow instructions from on-site staff, especially if parts of the beach are cordoned off for safety reasons.
Further updates will be provided once engineers have completed their assessment and any additional safety measures at Jackson’s Bay have been put in place.
Rockfalls are not unusual at cliff-backed beaches, particularly after periods of extreme weather.
Vale of Glamorgan Council has advised visitors to stay away from the cliff line at Jackson’s Bay until the ongoing assessment is complete.
