Guernsey police say the flight left Monday evening from Nantes en route to Wales with two people aboard.
A rescue helicopter and RNLI crews from Alderney and Guernsey were dispatched to search for the plane on Monday night.
'HM Coastguard helicopters from Solent and Newquay have been helping to search overnight with nothing found'.
Emergency services have reported that a small plane - a Piper Malibu - travelling from Nantes to Cardiff went missing near the Casquets lighthouse, and there are concerns that Sala was one of the two passengers on board.
Lifeboats and helicopters were sent out but the search was suspended four hours later as weather conditions worsened.
Fears were elevated when Cardiff Airport confirmed the aircraft was due to arrive from Nantes but had not, with a spokeswoman claiming that there were no further details.
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Ronaldo had been accused of defrauding authorities of £12.9m in unpaid taxes between 2011 and 2014, during his time with Real Madrid .
His mother, Mercedes, added: "The plane is from the President of Cardiff City FC, they informed us that the plane had disappeared and that they were looking for it".
Cardiff City said the club was "seeking clarification" as to what happened.
His signing, for a club-record fee of about £15 million, was considered a genuine coup for Cardiff, who had been monitoring the player for some time. The Guernsey Coastguard received an alert from Air Traffic Control at around 8:23 p.m. local time that the plane had gone missing from radar. "The aircraft was flying at 5000 feet." read the statement.
A search resumed at 08:00 GMT. Jersey ATC lost contact whilst it was flying at 2300 feet.
Another of Sala's former clubs, US Orleans, has tweeted their best wishes for the striker and the pilot, both of whom are still missing.
Sala had signed a three-and-a-half year deal with the Welsh club after scoring 12 Ligue 1 goals in 19 appearances this season.