Earlier this week, aid workers with the U.S.-based humanitarian organization Anera delivered about 47,000 hot meals to Palestinians in Gaza. It was a feat of logistics, says CEO Sean Carroll – and also not even close to enough.

“That portion of chicken and rice is probably going to be shared by at least two, maybe three or four or five family members, and will probably be the only meal of the day,” Carroll says. “And if that goes away, then it is not hyperbole to suggest that people could die of hunger or certainly the combination of thirst and hunger.”

Aid groups have been scrambling to mobilize whatever food stores are left within Gaza, while they wait for the governments in Israel, Egypt and the United States to arrange safe passage across the Egyptian border.

A deal struck on Thursday by Egypt and Israel and brokered by the United Nations to permit some aid to enter Gaza was characterized as “a start” by the World Health Organization. Bringing the aid to those in need will be “an absolute marathon,” Dr. Richard Brennan, the WHO’s Regional Emergency Director for the Eastern Mediterranean Region, told CNN. He noted that there are “a lot of complexities to getting this aid operation going.”

Israel has kept Gaza under “siege” since fighters with Hamas, which controls the Gaza Strip, attacked Israeli villages last week, killing more than 1,400 and taking nearly 200 hostages. Since then, the situation on the ground for besieged and hungry Gaza residents is growing increasingly desperate.

Bread is becoming especially scarce. The U.N.’s World Food Programme says that of the five flour mills in Gaza, only one is operating, due to fuel and energy shortages. Just five of the 23 bakeries WFP contracts with are open.

One aid worker in Gaza, a staffer for Islamic Relief Worldwide, says families are scraping together whatever food they can find. The worker asked to remain anonymous out of concerns for their safety ahead of a possible Israeli ground invasion.

“It takes 2 hours just to get some bread. The bakeries started giving people tickets for their share so that everyone can get some,” he said, communicating via an overseas colleague in response to questions from NPR. “My brother-in-law found [a shop] making falafel, which was previously very common but is now a big surprise. He bought some and made us all happy that night.”

Fresh water is also growing extremely scarce, the worker says.

“My mum tries to think of meals that would use less water to cook and less dishes to wash up,” the worker says. “”At my parents’ house there are around 20 children and 7 adults sheltering, so there is a huge demand for water for washing, cooking, cleaning. Even with so many people here we only flush the toilet twice a day – once in the morning, once at night.”

Even as people in Gaza try to stretch their meager food supplies, some 310 tons of food from the World Food Programme – enough fortified biscuits, date bars and canned fish to feed nearly a quarter-million people for a week – is sitting in a line of trucks at the Gaza border with Egypt. Other aid convoys waiting in Egypt carry medical supplies and drinking water. Planeloads of food from Dubai have been arriving at the nearby Egyptian city of Arish.

Just when and how much aid would be permitted under this week’s UN-backed agreement remains unclear. President Joe Biden said Thursday that aid could begin flowing as soon as Friday. However, at that time only 20 trucks – a fraction of the massed convoys – had been cleared to move once the crossing is opened. That has left the Rafah crossing a parking lot for humanitarian aid.

“The trucks [at the Rafah crossing] are cooling their heels. We have vehicles in convoy ready to roll that are not being permitted in,” says Steve Taravella, spokesperson for the World Food Programme.

Meanwhile, Gaza residents are increasingly desperate for food and water. Taravella estimates that the WFP has about two weeks worth of food supplies already placed inside Gaza and ready to distribute.

“People are definitely going hungry now. They are rationing out amongst themselves what they have been able to conserve,” says the WFP’s Taravella.

Aid groups unable to cross the border are working to apportion what limited food remains in Gaza to people in need. Sean Carroll of Anera says the Gaza shops and food retailers he works with are down to 2-3 days worth of food.

Lack of water, sanitation and nutrition also raise the risk for infectious disease outbreaks, in a territory where hospitals are already overwhelmed by the wounded.

Even before the current crisis, the population in the Gaza Strip was beset by food scarcity. The WFP estimates that a third of Palestinians in Gaza were food insecure already, which the WFP defines as people having to sell their possessions or use essential resources in order to subsist on a basic diet. Some 80% are considered in need of humanitarian aid.

In many cases, the workers who power the food-aid system in Gaza are themselves victims.

“Two of our staff lost several family members. One of them lost ten family members to a bomb and one lost 16 family members to a bomb,” says Sean Carroll, adding, “it’s hard to believe and understand that those words are true, even as I say them.”

Sean Carroll says of Anera’s 12 staffers in Gaza, nearly all have been evacuated to the south.

Bombing near the southern border with Egypt is further complicating efforts to open the way for aid. Humanitarian groups say even if the gates were flung open, it wouldn’t be safe to get the aid to people who need it.

With at least some aid expected to move as soon as the Thursday agreement takes effect, the World Food Programme and others are calling for a secure humanitarian corridor into Gaza, with safety guarantees that go beyond simply opening the crossing.

“A secure corridor is absolutely essential,” says WFP’s Taravella, “both a corridor into Gaza, but also a corridor or corridors within Gaza to help aid workers move around freely, to distribute this food and frankly, to help civilians feel safe and be safe to come out to seek food.”