The press release was not on the Academy's web page.
Swedish media outlets on Wednesday published what they reported were the seemingly leaked names of this year's Nobel chemistry prize recipients, hours before the laureates were to be announced.
Nobel leaks are rare, with the various prize-awarding academies going to great lengths to keep the winners' names under wraps until the announcements.
Sweden's paper of reference, Dagens Nyheter, and public broadcasters Swedish Television and Swedish Radio reported receiving a press release from the Royal Swedish Academy of Sciences that named three US-based chemists.
"We can't comment on this until we know what has happened, we have to look into it," the Academy's press spokeswoman Eva Nevelius told AFP.
According to the Swedish reports, the laureates are Moungi Bawendi from the Massachusetts Institute of Technology, Louis Brus from Columbia University and Alexei Ekimov who works at Nanocrystals Technology.
They had won the prize "for the discovery and synthesis of quantum dots", according to the reports.
The press release was not on the Academy's web page.
The Academy was due to make its announcement at 11:45 am (0945 GMT), minutes after holding a meeting and a vote to pick the winner.
Heiner Linke, an expert on the Academy's Nobel Chemistry Committee, expressed surprise to Dagens Nyheter.
"Right now I'm just trying to understand what has happened. We haven't made a decision yet, so if a press release has gone out then it's definitely a mistake," Linke said.
The list of nominations for each prize is also kept secret for 50 years.
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