The Air Accidents Investigation Branch (AAIB) was advised by its French counterparts on Monday that part of a cushion was found on a beach near Surainville on the Cotentin Peninsula.
A second cushion was found in the same area later that day.
The AAIB said in a statement: “From a preliminary examination we have concluded that it is likely that the cushions are from the missing aircraft.”
Sala, 28, was being flown to the UK by Dave Ibbotson, a 60-year-old pilot from Crowle in Lincolnshire, when the single-engined Piper PA-46 Malibu lost contact with air traffic controllers near Alderney earlier this month.
The 28-year-old Argentinian was due to start training at Cardiff the following day after his disappearance, having signed a £15 million transfer deal from French club Nantes.
The striker reportedly voiced fears about the safety of the missing plane in an audio message he sent to friends in France during the flight.
The AAIB has established a “priority search area” of around four square nautical miles and commissioned a specialist vessel to carry out a survey of the seabed.
It would not confirm the location, but said it is where it believed the aircraft entered the sea.
Due to the weather and sea conditions, this is expected to start at the end of this weekend and could take up to three days.
If wreckage is found, a remotely operated vehicle will be used to examine it.
The AAIB said it was aware that a privately-funded search was also being conducted and is “liaising closely with those involved to maximise the chance of locating any wreckage and ensure a safe search operation”.
Marine scientist David Mearns is assisting the family of footballer Sala, who had just signed for Cardiff City, with this separate search.
He said on Monday it would focus on an area of 25 square nautical miles on the seabed north of Alderney.
The Piper PA-46 Malibu carrying Sala and pilot David Ibbotson disappeared over the English Channel on January 21 after leaving Nantes in France for Cardiff.
It requested to descend then lost contact with Jersey air traffic control.