One person is believed to be trapped under rocks after a landslide at a beach.
Police, the fire service, ambulance service and the Coastguard were dealing with the incident near the Freshwater Beach Holiday Park at Burton Bradstock, near Bridport, Dorset.
Witnesses said there had been one death at the site, which is known locally as Hive Beach, following a "significant rockfall".
The Maritime and Coastguard Agency said Portland Coastguard was told a person was trapped under the fallen rocks between Freshwater and Burton Bradstock in an emergency call received just before 12.30pm on Tuesday.
The incident comes two weeks after Somerset couple Rosemary Snell, 67, and Michael Rolfe, 72, were killed in a landslide at the Beaminster Tunnel just nine miles away.
In a joint statement Dorset Police and Dorset Fire and Rescue Service said: "Officers, with assistance from the police helicopter, are currently working alongside Dorset Fire and Rescue Service and other agencies to search the area. The Urban Search and Rescue Team (USAR) from Devon and Somerset has also been deployed to this incident. This is a national resource."
The Maritime and Coastguard Agency said three Coastguard rescue teams and the Coastguard rescue helicopter based in Portland were at the scene in Lyme Bay.
A spokeswoman said: "West Bay, Lyme and Wyke Coastguard Rescue Teams and their managers are currently on scene with the Coastguard rescue helicopter based in Portland.
"They are working with Dorset Police, Dorset Fire and Rescue Service, South Western Ambulance Service and the lifeboat from Lyme Regis to search for those who may be trapped and to keep the public away from the area surrounding the landslide."
A National Trust spokesman said: "Our thoughts are with all those involved in this tragic accident. "Coastlines are dynamic and changing environments and it is impossible to predict when these kinds of events might occur. National Trust land at Burton Bradstock will remain closed whilst we assist the emergency services in whatever way we can."