A mysterious mayday call saw both Falmouth lifeboats launched on Monday to search for an unknown vessel somewhere in the bay.

The spoken word mayday was broadcast three times on VHF channel 16 just before 10.20am.

Falmouth Coastguard requested the launch of the inshore lifeboat at 10.26am and she headed out into the bay to start a search of the coastline.

At 10.40am after working her way towards the Helford and the Manacles the inshore lifeboat requested the launch of the all weather lifeboat "due to the area being covered and the number of boats afloat," an RNLI spokesperson said.

The search was terminated at 11.33am when both lifeboats had covered their designated areas without uncovering the source of the distress call.

"The source of the mayday calls remains a mystery," the RNLI spokesperson said, "while it was not heard by the coastguard at Pendennis Point and many other vessels it was heard by a merchant vessel and a yacht so a search was commenced."