Premier League club Cardiff City's record new signing, Argentina-born striker Emiliano Sala, was on board a light aircraft that disappeared over the English Channel on Monday night, police sources told AFP.
Sala, signed by Cardiff on Saturday from French club Nantes for a reported 17 million euro ($19.3 million) fee, was flying to Cardiff aboard a small plane that disappeared from radars around 20 kilometres (12 miles) north of Guernsey, sources confirmed on condition of anonymity.
A statement from police on Guernsey, a British island just off the coast of France, said lifeboats and a helicopter had searched for several hours for the plane, which had two people and a pilot on board.
"The search was terminated at 02:00, with all search and rescue assets being stood down, due to strengthening winds, worsening sea conditions and reducing visibility," the statement said.
"At this time no trace of the missing aircraft had been found," it added.
Two helicopters, two planes and a lifeboat joined renewed efforts on Tuesday morning to find the single-propeller plane which is thought to have crashed.
Sala, 28, who had been at Nantes since 2016 and had scored 13 goals in all competitions this season, had signed a three-and-a-half-year contract with relegation-threatened Cardiff subject to receiving international clearance.
Neither club has commented publicly on the disappearance, but Nantes have postponed their French Cup match against third-tier side Entente SSG on Wednesday as a mark of respect.
When he put pen to paper at Cardiff on Saturday, Sala, who also has Italian nationality, said in a statement: "I'm very happy to be here. It gives me great pleasure and I can't wait to start training, meet my new team-mates and get down to work.
"For me it feels special (to be the club's record signing). I have come here wanting to work and to help my team-mates and the club."
Sala's last post on Instagram showed him surrounded by players from FC Nantes. "La ultima ciao (the last goodbye)," he wrote.
The accident, if confirmed, would come only three months after the Thai billionaire owner of Leicester City football club died in a helicopter crash that shocked the club and supporters around the world.
Vichai Srivaddhanaprabha and four others died on October 28 shortly after taking off from the pitch of the club's stadium in central England.
Disconnected cockpit pedals, which are used to control the rotor on the helicopter's tail, were found to be the cause of the accident by investigators.
Cardiff currently sit third from bottom of the English Premier League with 19 points.