GAZA: Growing numbers of Palestinians are fleeing their homes for makeshift shelters in schools, office buildings and a park as the Israeli Army continues to press its military campaign deeper into the city of Gaza.

According to the United Nations, about 30,000 people are living in schools it sponsors, and an estimated 60,000 have fled to the houses of relatives. The figures represent a small part of Gaza's 1.5 million population but have doubled in the past four days, UN officials said, raising concerns about the humanitarian impact of a broader war.

"What began as very small, isolated numbers is now turning into a torrent," said Aidan O'Leary, deputy director for the UN agency that deals with Palestinian refugees.

Major Jacob Dalal, an Israeli military spokesman, said units used leaflets to warn families to leave areas where they planned to operate.

Aid officials say that with Gaza's borders closed, choices for shelters in the 360-square-kilometer, or 140-square-mile, strip are slim and not completely safe. Last week, as many as 43 people were killed at a UN school by an Israeli mortar fired, the military said, in response to a Hamas attack. The Israeli military disputes the death toll.

Aid groups have been pointing to what they say is a growing number of refugees. When Israeli soldiers moved deeper into the Zeitoun neighborhood on Sunday night, Olfat Jaawanah decided she had had enough. Shrapnel flew through a window, wounding her son, Ali, she said, and on Monday morning, she gathered a few blankets and moved her nine children out of their large house.

The nearby UN school was full - its bare classrooms packed with families and its toilets fetid - so she brought her family instead to her husband's office, a building belonging to an international organization in the center of Gaza, the strip's main city.

According to O'Leary, about a third of the agency's 91 schools are now full.

"Explosions, rockets," she said, arranging her children's clothes. "We can't take it anymore."

Movement is complicated by the confusion over when it is safe to leave. When the Abu Hajaj family received a leaflet last weekend, they took it as a sign of safe passage.

But Majad Abdel Karim Abu Hajaj, a teacher at a UN school, said his mother and sister were killed as they walked holding a white flag. Their bodies remain where they fell, he said, because ambulances cannot get to the area.

Sarit Michaeli of B'Tselem, an Israeli human rights group, said she had had six reports of families stuck in areas now occupied by Israeli troops.

At times, the city took on a surreal quality. A woman came with a pan and dough to Al Nasir hospital, asking for the use of their electricity so she could bake. A corpse was wheeled in a donkey cart where an ambulance was afraid to go.

Humanitarian shipments were moving on Monday, and Egypt, under pressure to do more for Palestinian victims, agreed to allow in 38 Arab doctors and a group of European lawmakers.

Palestinians interviewed in Gaza on Monday cited another reason for their flight: Israeli soldiers, they allege, are firing rounds of a noxious substance that burns skin and makes it hard to breathe.

A resident in the southwest part of Gaza on Monday showed a reporter a piece of metal casing with the identifying number, M825A1, which Marc Garlasco, a military analyst with Human Rights Watch, identified as white phosphorous. It is typically used for signaling, producing smoke screens and destroying enemy equipment.

In recent years, military experts and human rights advocates have argued over whether its use to harm people violates international conventions.

Dallal would not say whether Israel was using white phosphorous but said: "The munitions we use are consistent with international law."

Still, white phosphorous causes injury, and a growing number of Gazans report being hurt by it in Beit Lahiya, Khan Yunis, and in eastern and southwestern Gaza City. When exposed to air, it ignites, the group says, and if packed into an artillery shell, it can rain down flaming chemicals that cling to anything they touch.

Luay Suboh, 10, from Beit Lahiya, lost his eyesight and skin on his face Saturday when, his mother Siham said, a casing clung to him as he darted home from a shelter where his family is staying.

The substance smelled like burned trash, said Jaawanah, the mother who fled her home in Zeitoun, who had experienced it too.

She had no affection for Hamas, but her sufferings are changing that.

"Do you think I'm against them firing rockets now?" she asked, referring to Hamas. "No. I was against it before. Not anymore."