The captives are expected to be freed every day until Monday during the lull in fighting.
US President Joe Biden has said there is a “real” possibility that a four-day pause in Israel’s war on Gaza will be extended.
“I think the possibilities are real,” he told reporters on Friday, while declining to speculate on how long the war that began Oct. 7 after a surprise Hamas attack inside Israel could last.
“My expectation and hope is that as we move forward, the rest of the Arab world and the region are also putting pressure on all parties to stop this, to end it as quickly as possible,” Biden said, while reiterating his support for Israel.
He stressed that “eliminating” Hamas remains a “legitimate” mission for Israel.
He said only that he had “encouraged” Israeli Prime Minister Benjamin Netanyahu to try to limit civilian casualties.
Some 15,000 Palestinians, most of them women and children, have so far been killed in Israeli bombings following the Hamas attack that killed 1,200 people in Israel.
Under the terms of the truce, which took effect early Friday, 50 women and children detained in Gaza will be freed within four days, in exchange for 150 Palestinian women and children who are among the thousands imprisoned in Israeli jails.
On Friday, 39 Palestinians were freed in the occupied West Bank in exchange for Hamas releasing 24 captives, including 13 Israelis. More are expected to be released Saturday afternoon.
After the release of the first captives held by Hamas, Biden said: “It’s just the beginning, but so far it’s been going well.”
Both Israel and Hamas have vowed to keep fighting, but Israel has signaled it is open to extending the truce if more captives are freed at a rate of 10 a day, something Biden said he hoped would happen.
Hamas has said the non-civilian Israelis it is holding will only be exchanged for the thousands of Palestinians languishing in Israeli prisons under harsh conditions, many of them held without charge.
Some 200 trucks carrying humanitarian aid also arrived in the besieged enclave as part of the truce on Friday, and on Saturday the first deliveries arrived in northern Gaza since the start of the war.
But the level of destruction remains high in both the north and south of the Gaza Strip, and the United Nations confirmed on Friday that Israel significantly increased its attacks on Gaza before the truce took effect.