Under the terms of the October ceasefire deal, Hamas had handed over remains described by the Red Cross as those of one of the last two deceased hostages still in Gaza.
Israeli forces said they sent for forensic testing the remains handed over on Tuesday, which they described as "findings".
"The findings brought yesterday for examination from the Gaza Strip are not linked to any of the deceased hostages," Prime Minister Benjamin Netanyahu's office said in a statement on Wednesday.
The identification had been made at the National Center for Forensic Medicine, it said.
The Al Quds Brigades - the armed wing of the Hamas-allied Palestinian Islamic Jihad movement - said later on Wednesday it was searching for a body of a hostage in northern Gaza, along with a team from the Red Cross.
It did not say which of the two remaining deceased hostages it was searching for.
The two are Israeli police officer Ran Gvili and Thai national Sudthisak Rinthalak, both kidnapped during Hamas' October 7, 2023, attack on Israel that touched off two years of devastating war in Gaza.
The Geneva-based Red Cross has acted as an intermediary between Gaza militant groups and Israel throughout the war triggered by Hamas's attack, helping to pave the way for the release of living hostages and the handover of remains.
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