Currently, Hamas is holding 51 Israeli hostages alive, according to Israeli analysts. The remaining Israeli hostages are dead, although it has not been officially announced that they are all dead, as reported this morning by Israel Hayom.
About two months ago, Prime Minister Benjamin Netanyahu said in a briefing before the Knesset's Foreign Affairs and Defense Committee that half of the hostages are alive.
The data on which Netanyahu relied was compiled based on information accumulated through various channels since October 7, some of which are public and some are based in military intelligence. This means that 50 of the Israeli hostages held in Gaza are dead, although so far only 37 hostages have been officially declared dead with their bodies held by Hamas.
It was also reported that this gap is explained in Israel by the fact that declaring death requires absolute evidence, on the basis of which medical and rabbinical authorities can declare a person's death. Such evidence does not exist at the scientific or religious level required for a formal declaration of death, but it seems that Israel has enough information to assess that additional hostages are dead already.