A chess player at the centre of a cheating row gripping the game "likely" cheated in more than 100 games online, according to an investigation, reports BBC.
Hans Niemann has been accused by world champion Magnus Carlsen of cheating, though no evidence has been presented.
Now an investigation by Chess.com says it is likely Niemann has cheated "much more often" than he has acknowledged.
But it found no evidence he had cheated in his game against Carlsen or in any "over-the-board" games.
The American has admitted cheating in informal games when he was younger but denies doing so in competitive games.
The 19-year-old, who has been approached by the BBC for comment, has previously accused Carlsen and Chess.com of trying to ruin his career.
The scandal began earlier this month after Carlsen, considered by many to be the greatest player of all time, was defeated by Niemann at the Sinquefield Cup in a major upset.
The Norwegian made veiled accusations of cheating against Niemann at the time before openly accusing him last week.
Now Chess.com has produced a 72-page investigation into Niemann's games on the site, which most of the world's top players compete on, including for cash prizes.
The site, which has banned Niemann for alleged cheating, claims it is likely he cheated as recently as 2020, including in prize money events and against highly-rated "well known" figures in the game.
Its analysis compared Niemann's moves to those suggested by chess computers - which are far stronger than even the best players - and the probability of his results, among other factors.
"Overall, we have found that Hans has likely cheated in more than 100 online chess games, including several prize money events," the report said.
"He was already 17 when he likely cheated in some of these matches and games. He was also streaming in 25 of these games."
The report contradicts statements previously made by Niemann that he had only cheated in informal games on the site when he was 12 and 16, but never in competitive games or when he was streaming on gaming platforms such as Twitch.
However, although his results are "statistically extraordinary", Chess.com said there was no "direct evidence" Niemann had cheated in his win against Carlsen or in other over-the-board games in the past.
In his statement last week, Carlsen suggested Niemann had cheated in their game at the Sinquefield Cup in the US state of Missouri, saying he "wasn't tense or even fully concentrating" while outplaying him using the black pieces "in a way I think only a handful of players can do".
He also said he had become suspicious of Niemann because he has made "unusual" progress in recent years. Others have argued that Niemann's progress, while fast, is comparable to other top junior players.
Chess.com said there were "certain aspects" of the game that were "suspicious", including Niemann's explanation of the game afterwards.
The site also noted "anomalies" in Niemann's rate of improvement, which has seen him soar up the rankings in classical chess from around 800 in the world to the top 50 in less than two years.
Chess.com said this rise was the fastest in "modern recorded history" and had occurred "much later in life than his peers".
The site also denied it had been pressured by Carlsen, who has dominated chess for more than a decade, to remove Niemann.
Carlsen has insisted he will not play Niemann, and earlier this month resigned in protest after just one move when they re-matched each other in an online tournament.
When the controversy erupted earlier this month, Niemann issued a strenuous denial, saying he was willing to play naked to prove he was not concealing electronic devices that could allow him to cheat.
"I don't care, because I know I am clean. You want me to play in a closed box with zero electronic transmission, I don't care. I'm here to win and that is my goal regardless."
A statistical analysis of Niemann's over-the-board games by Prof Kenneth Regan, widely regarded as the world's leading expert on cheating in chess, found no evidence he had cheated.