Under the first phase of the ceasefire deal, which took effect on 10 October, Hamas agreed to return the 20 living and 28 dead Israeli and foreign hostages it was holding within 72 hours.
All the living Israeli hostages were released on 13 October in exchange for 250 Palestinian prisoners and 1,718 detainees from Gaza.
Israel has handed over the bodies of 285 Palestinians in exchange for the bodies of the 19 Israeli hostages returned by Hamas, along with those of three foreign hostages - one of them Thai, one Nepalese and one Tanzanian.
Five of the six dead hostages still in Gaza are Israelis and one is Thai.
Israel has accused Hamas of deliberately delaying the recovery of the bodies, while Hamas has insisted it is struggling to find them under rubble.
The slow progress has meant there has been no advance on the second phase of President Donald Trump's Gaza peace plan. This includes plans for the governance of Gaza, the withdrawal of Israeli troops, the disarmament of Hamas, and reconstruction.
All but one of the dead hostages still in Gaza were among the 251 people abducted during the 7 October 2023 attack, during which about 1,200 other people were killed.
Israel responded by launching a military campaign in Gaza, during which more than 68,800 people have been killed, according to the territory's Hamas-run health ministry.