JERUSALEM — Palestinians began to absorb the scale of damage to their neighborhoods in the Gaza Strip on Monday afternoon, while Israelis waited anxiously for news about the condition of three newly released hostages, as a day-old ceasefire between Hamas and Israel continued to hold.

Palestinians picked their way through vast swaths of rubble, trying to salvage undamaged belongings — a sofa, a mattress, a chair, a crate — from the wreckage of their former homes and neighborhoods that have been decimated by 15 months of war. Gaza Civil Defense, an emergency service, announced that nearly half of its employees had been killed, wounded or detained during the war.

The scenes embodied the bittersweet emotions felt on either side of the Israel-Gaza border. Palestinians celebrated Israel’s release of 90 Palestinian prisoners early Monday, hours after Hamas freed three Israeli hostages in Gaza, setting off joyous reunions with their families. The exchange capped the first of what is hoped will be a series of weekly hostage-for-prisoner swaps over the next six weeks.

As the truce went into effect Sunday, celebrations replaced explosions and hundreds of humanitarian aid trucks began rolling into Gaza. The three hostages returned to jubilant embraces with relatives and friends at an Israeli hospital, while fireworks and cheering crowds greeted the newly freed Palestinian prisoners in the Israeli- occupied West Bank.

But the joy was shadowed by uncertainty and expectations of prolonged hardship to come, with no comprehensive plan in place for how Gaza will be rebuilt. Palestinians returning to Rafah, a southern city, found it mostly flattened by fighting; the mayor said 60% of homes and 70% of the city’s sewage system had been destroyed.

After months of lawlessness in Gaza that reduced humanitarian aid to a trickle, aid agencies have warned they need unimpeded access for supplies to reach those in need.

In Israel, little was announced about the health of the hostages released Sunday, while nothing is known about the identities of four hostages expected to be freed next weekend in exchange for additional Palestinian prisoners. If the deal holds, 33 of the 100 remaining hostages still in Gaza, living and dead, and more than 1,000 imprisoned Palestinians held in Israel will be released over the first six weeks of the ceasefire.

But the fate of more than 60 other hostages and thousands of other Palestinian detainees depends on the deal’s extension.

Hours after the ceasefire between Israel and Hamas took effect, a senior Hamas official said that the militant group was ready to start a dialogue with the United States, making a rare overture to a country that Hamas has long excoriated for supporting Israel.

The comments made by the official, Mousa Abu Marzouk, who is based in Qatar, suggest that at least some senior members of Hamas hope it can engage directly with the Trump administration even though the United States has designated Hamas as a terrorist organization since 1997.