LONDON — Before the plane carrying him vanished over the English Channel, an Argentine soccer player sent a chilling audio message from the flight in which he said “I’m so afraid” and warned that the aircraft “seems like it’s falling to pieces,” Argentine news outlets reported on Tuesday.Both Emiliano Sala, 28, who had just signed with Cardiff City of the English Premier League, and the pilot, who has not been publicly identified, were feared dead after the disappearance of the plane Monday night.A joint French and British search effort resumed on Wednesday with airplanes, helicopters and ships, but officials have said that if the missing plane went down in the cold, rough waters, there was little chance that the two people aboard were still alive.While in the air, as the plane was battered by harsh weather, Mr. Sala, speaking in Spanish, sent an audio WhatsApp message to a group of friends, said Diego Rolán, a Uruguayan player, who told a radio station in his home country that he was among the recipients of the message. Argentine news organizations obtained and posted on their websites what they said was Mr. Sala’s recorded message.The man speaking sounds calm, asking his friends how they are doing, looking forward to joining his new team, complaining of being tired, and even yawning. But he also returns several times to his concern about the flight.“If, in an hour and a half, you have no news from me, I don’t know if they are going to send someone to look for me, because they are not going to find me,” he says.Mr. Sala became a star playing for Nantes in the top French league, and the team’s fans gathered in his honor in the city’s Place Royale on Tuesday night, chanting and waving banners. He was recently sold to Cardiff City, and he was scheduled to join that team on Tuesday.Mr. Sala was flying to Cardiff from Nantes aboard a single-engine, propeller-driven Piper Malibu, on a night when the region was hit by rain, snow and high winds. The plane took off at 8:15 p.m. local time and disappeared from air traffic control radar over the Channel 68 minutes later.French aviation officials have said that only two people were aboard, but there have been unconfirmed reports in the news media of another passenger.In a statement, the harbormaster for the island of Guernsey, Capt. David Barker, listed four theories about what happened. Two seemed especially remote possibilities: that the men on the plane had touched down safely on land somewhere, or that they were rescued from the sea by a passing ship, but had not gotten word out that they had survived.The other possibilities were less optimistic: that “they landed on water and made it into the life raft we know was on board,” or that “the aircraft broke up on contact with the water, leaving them in the sea,” Captain Barker said.“Our search area is prioritized on the life raft option,” he said.