Solent Coastguard Maritime Rescue said it had received information that a person onboard the Celebrity Eclipse cruiser had plummeted into the channel around eight miles north of Cherbourg.
A spokesman said that that French authorities were currently dealing with the incident, which occurred late on Friday night.
The liner, owned by travel company Celebrity Cruises, is believed to have been travelling between Cherbourg and Southampton.
French officials said they had deployed teams of emergency workers to the incident, but said they were unsure of the exact details and refused to confirm if a person had fallen into the sea. Source