There has been a "substantial" cliff fall at Porthtowan beach with further falls expected, according to emergency services.
On Monday afternoon coastguards cordoned off the path above the fall and advised people to stay clear of the area.
A spokesperson for St Agnes Coastguard Search and Rescue Team warned: "This cliff is very unstable and we expect more will fall within the next few days or weeks."
The coastguard said beach users should remain a distance of at least the height of the cliff away.
The team was mobilised to the beach at 13:49 GMT to what it called a "substantial" cliff fall.
The coastguard shared photos of the crumbled cliff on social media, advising beachgoers against exploring the area because of the risk of further falls.
"If a cliff fall does occur and you suspect that someone has been injured, call 999 immediately," it added.