The window for Palestinians to evacuate from northern Gaza is closing rapidly, with almost no time remaining for civilians to move through approved corridors ahead of an anticipated military operation from Israel.

Avichay Adraee, a spokesperson for the Israel Defense Forces (IDF), said Palestinians had until 4 p.m. local time to evacuate through two main roads in northern Gaza and head south.

With the deadline just passing as of this publication, the window appears to have been closed, at least technically.

But many Palestinians are still fleeing and it’s unlikely Israel is already closing it up.

The U.S. is trying to move Palestinian Americans through the Rafah crossing, which connects with northeast Egypt, according to several media reports. But the crossing is closed on the Palestinian side because of Israeli strikes.

Israel on Friday ordered more than one million Palestinians in Gaza to evacuate, issuing the warning by dropping fliers and leaflets.

The order to evacuate was criticized by the United Nations, which warned it could be disastrous for Palestinians, who are blockaded by land, air and sea and have been under complete siege for days.

The U.N.’s humanitarian office said tens of thousands of Palestinians have fled in Gaza and at least 400,000 have been displaced because of the war Israel is waging against the Palestinian militant group Hamas.

Israel is vowing fierce retribution against Hamas for raiding their southern border and killing more than a thousand people in a surprise last week last week.