A U.N. official who took part in a humanitarian aid convoy to northern Gaza said on Sunday that aid groups were on track to deliver the biggest shipment in over a month, describing thin, gaunt residents slaking their thirst as soon as water arrived.

Before a four-day truce between Israel and Hamas got underway on Friday, U.N. agencies had voiced fears of disease and dehydration in the north, cut off from outside aid for weeks in a siege within a siege. The UN previously said it could not get safe passage and medical groups who remained active like the International Red Cross came under fire there.

“People are so desperate and you can see in adults’ eyes they haven’t eaten, you can see the children are getting thinner,” the U.N. children’s agency’s James Elder told Reuters by video link from southern Gaza after returning from Gaza City.

“There’s just this immense relief. Literally, people as they get water start drinking the water immediately,” he said. “They’re thirsty. They’ve been thirsty for days.”

UNICEF’s Elder took part in a five-truck convoy on Sunday alongside other U.N. agencies delivering high-energy biscuits, vitamin tablets for children as well as medical kits. A dispute over aid flows to the north of the Israeli-besieged enclave temporarily held up a deal to free captives on Saturday.

The deliveries were made to hospitals where rations were controlled, Elder said. He described seeing children, often with multiple injuries including burns and shrapnel wounds, lying in hospital beds in a state of shock. “They look like they’d been broken and then badly put back together,” he said.

“It seems callous and cold to think that we may be getting to the end of those deliveries and hostilities will continue, (that) the war, this war on children will continue.”

Even as the aid deliveries flowed north, Elder said he saw hundreds of Gazans heading in the other direction, fearing the renewal of Israeli bombardments if the four-day truce is not prolonged. “People are so terrified that this pause won’t be continued … I saw grandmothers carrying children, children pushing grandmothers in wheelchairs through the dust,” he said.