(NewsNation) — While the border crossing between Egypt and Gaza has opened to allow humanitarian aid in, Americans aren’t being allowed out.

National Security Council spokesman Adm. John Kirby says the United States is “hard at work” to get trapped citizens back home.

“We know there’s several hundred (Americans in Gaza). We know that dozens and dozens are, we think, are down there near the Rafah crossing ready to come out … we’ve just got to make sure we get a process in place to allow them to do that,” Kirby said Monday on “Elizabeth Vargas Reports.” “It has been a consistent focus area for us.”

The effort to get Americans out of Gaza comes as Hamas on Monday released two elderly Israeli women who were being held captive. Hamas said it had released the female civilians, identified as Nurit Cooper, 79, and Yocheved Lifshitz, 85, in response to Egyptian-Qatari mediation efforts.

Meanwhile, the Biden administration says there are 10 Americans who are unaccounted for more than two weeks after the Oct. 7 attack on Israel by Hamas.

“We don’t know whether they are deceased, whether they are just missing somewhere, or whether in fact they could be held hostage by Hamas — it’s entirely possible that some of them are,” Kirby said. “We’re just trying to get as much information as we can.”

The situation in Gaza is worsening as Israel calculates when to roll its troops across the border and fight Hamas. Inside Gaza, women, children and the elderly are among the hundreds rushing into the hospitals that are left trying to get care.

On Monday, a third small aid convoy from Egypt entered Gaza, where the population of 2.3 million has been running out of food, water and medicine under Israel’s sealed border. With Israel still barring entry of fuel, the U.N. said its distribution of aid would grind to a halt within days when it can no longer fuel its trucks. Gaza hospitals flooded by a constant stream of wounded are struggling to keep generators running to power lifesaving medical equipment and incubators for premature babies.

Kirby acknowledged that there is an “acute need for fuel” inside Gaza but said it’s imperative it doesn’t end up in the hands of Hamas.

“There is a desperate, legitimate need for fuel, and we are working hard with partners to see what we can do to break that logjam,” Kirby said. “We recognized that the trucks that are going in, while it’s terrific they’re moving, there’s too few of them … and we’re working hard to see if we can’t increase and sustain the humanitarian assistance that’s so desperately needed inside Gaza.”

The Associated Press contributed to this report.