An air and sea search was underway on Sunday night for a passenger who is believed to be missing overboard.
The crew of the Condor Rapide Fast Ferry, which was en route from Guernsey to Poole in Dorset, raised the alarm at 5.35pm.
British and French coastguard, as well as lifeboats from Weymouth and Alderney and a search plane from the Channel Islands, are searching the route of the ferry to find the missing passenger, a spokeswoman for the HM Coastguard said.
A spokesman for Condor Ferries said: "At 5.35pm today crew were made aware of a possible missing person situation onboard Condor Rapide.
"The captain raised a Pan Pan with the coastguard and a full search was conducted of the vessel.
"The passenger was unable to be found and the Pan Pan was upgraded to a Mayday."
The statement continued: "Condor Rapide is currently engaged in searching the area where the passenger is believed to have gone missing, and Portland Coastguard is co-ordinating.
"The Portland Coastguard helicopter has been scrambled and other vessels in the area are participating in the search.
"The ferry was en route from Guernsey to Poole."