The wreckage of the plane that went missing off Guernsey while carrying Argentine striker Sala, 28, and pilot David Ibbotson, 59, was found on the seabed of the English Channel on Sunday.
With a preliminary examination earlier this week drawing a conclusion that two parts of seat cushions that had been found "likely" came from the disappeared plane, the AAIB chose to commission a specialist survey vessel to carry out an underwater survey of the seabed to try to locate and identify possible aircraft wreckage.
The Piper Malibu N264DB carrying Sala, 28, and pilot David Ibbotson, 59, was discovered off the coast of Alderney in the English Channel on Sunday evening - nearly two weeks after it disappeared.
According to the statement made by the Air Accidents Investigation Branch as quoted by Metro news, a body has been discovered in the wreckage of the aircraft underwater.
"Tragically, in video footage from the ROV, one occupant is visible amidst the wreckage", the statement read.
The Air Accidents Investigation Branch (AAIB) confirmed on Monday that a body is visible in the wreck, which is about 67m deep.
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Two vessels, including one commissioned by the AAIB, had been taking part in a fresh search covering an area of around four square nautical miles on Sunday when the wreckage was located.
He said that: "I can not believe it".
Prior to Sunday, the previous significant update from the AAIB had come when seat cushions thought to be from the plane were found on a beach in northern France on Wednesday. When contacted by Argentina's Cronica TV, Sala's father, Horacio, was in disbelief over the news, saying it was "a bad dream".
"As agreed with the AAIB they moved the GEO OCEAN III over the position we provided them to visually identify the plane by ROV [remotely operated vehicle]".
"Mr Mearns added: "(The AAIB) will be able to rule things out or rule things in, that's the normal investigative process for any crash, so I think it's imperative that the plane is recovered, and now even more so now we know someone is down there". "But tonight they have heard devastating news and in respect of the families I won't comment any further about what has happened".
Cardiff City supporters paid tribute to Emiliano Sala on Saturday in emotional scenes before the Welsh club won their Premier League clash with Bournemouth. "In 25 metres to 30 metres of water, it would be a lot easier, but in 70 metres, it would be a much bigger operation".