France's Civil Aviation Authority says Cardiff City footballer Emiliano Sala was aboard small plane missing in the channel.
Air Traffic Control said the aircraft was travelling from Nantes in western France to Cardiff when it went missing.
Concerns were raised when the 28-year-old Cardiff forward failed to respond to messages on social media after reports he had been travelling to the UK on Monday.
The Argentinian made club history when he was bought for a record fee of £18m on a three-and-a-half year deal from Nantes at the weekend.
In one of his last social media posts, he shared a photo with his former teammates, writing "Ciao" and adding heart emojis.
He had played in France since 2012.
Cardiff City chairman Mehmet Dalman has released a statement saying: “We are very concerned by the latest news that a light aircraft lost contact over the Channel last night. We are awaiting confirmation before we can say anything further. We are very concerned for the safety of Emiliano Sala."
Emiliano's former club Nantes posted a video yesterday saying thank you for his services following his move to Cardiff.
What we know so far is that at least two people are thought to be on board the Piper Malibu plane which lost contact near the Casquets lighthouse yesterday.
A coastguard rescue helicopter and crews from Alderney and Guernsey RNLI have joined the search in the area around the lighthouse.
HM Coastguard said the disappearance was not in the UK search and rescue area but it had sent two helicopters to help.
"HM Coastguard are currently assisting Guernsey Coastguard with a search for a light aircraft off Alderney in the Channel Islands," a spokeswoman said.
"HM Coastguard helicopters from Solent and Newquay have been helping to search overnight with nothing found."