The coastguard and other emergency services are dealing with a major landslip at Monmouth Beach in Lyme Regis. Portland Coastguard say 150m of cliff has collapsed.
They are working to see if anyone has been caught up in the cliff fall.
Police are warning people who own chalets on Monmouth Beach in Lyme Regis not to visit them under any circumstances because of the risk from landslips.
It comes after a fresh fall closed the access road to the beach indefinitely. Officers are warning visitors not to cross the police tape as there is a considerable danger of more landslips.
The beach is about 12 miles from Burton Bradstock where a 22-year-old woman died in a cliff collapse last July.