OSLO — The protocol for nominating and choosing recipients of the Nobel Peace Prize is one of the world’s most scrutinized and secretive.

A total of 329 candidates — 217 individuals and 112 organizations — are being considered for this year’s prize, which will be announced in October. The identities of the candidates are kept secret, and indeed, the Norwegian Nobel Committee, which awards the prizes, is forbidden from divulging any information about its deliberations for 50 years, and even then, only for scholarship purposes and at its discretion.

But a wrinkle in this time-honored process — the peace prize was first awarded in 1901 — emerged on Tuesday, when the committee announced that it had uncovered what appeared to be a forged nomination of President Trump for the prize. The matter has been referred to the Oslo police for investigation.

Moreover, the forgery appears to have occurred twice: Olav Njolstad, the secretary of the five-member committee, said it appeared that a forged nomination of Mr. Trump for the prize was also submitted last year — and was also referred to the police. (The earlier forgery was not disclosed to the public at the time.)