A man was seen hurling stones from the top West Bay's cliffs onto the beach below.
Police say the man's actions could have killed someone.
The man was spotted by anglers repeatedly sitting and standing on the cliff edge and throwing stones onto the beach shortly before 9pm last night.
They called the coastguard because of their concern for the man and the danger of the rocks being thrown.
Coastguard teams from Bridport and Lyme Regis, along with the Lyme Regis RNLI inshore lifeboat, attended.
A thorough search on the cliff top and beach was made but the man was not found.
A spokesman for Bridport Police said: "If you see people throwing stones from the cliff top onto the beach then call the police at the time as this behaviour is dangerous and could be potentially fatal should they hit someone."
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