The Israelis admit firing 200 white phosphorous shells, but deny breaking international law.
The last bombing raid in one part of Gaza was a week ago. The area is littered with pieces of shrapnel and bits of sticky, gummy brown material.
Rub it and it bursts into flame and emits an acrid smoke. That's a distinct characteristic, experts say, of white phosphorous.
Sabbah Halima's blister-covered hands are an example of the kind of wound white phosphorous inflicts.
"In hours it becomes much deeper and much whiter, plus smoke comes out of the wound," said Dr. Nafez Abu Shaaban, chief of the burn unit at Shifa Hospital.
The United Nations refugee agency says white phosphorous hit its warehouse in the city center.
"I think our people have said if it looks like white phosphorous, if it acts like white phosphorus, it must be, white phosphorous," said Karen AbuZayd, UNWRA Commissioner-General.
Jodie Clark, a logistics officer for UNWRA, risked her life to pull a burning shell from under a fuel tanker.
"As I ran to the workshops another shell landed probably 30 meters in front of me and then just fireworks burst up from the ground and sprayed pellets of a burning substance all over the place," Clark said.
Pizzey showed part of one of the shells.
"The fire extinguisher didn't put it out, it continued to burn and in fact when we went back an hour later to fight the rest of the fire it was still burning," Clark said.
The Israelis have ordered an inquiry. But human rights groups are calling for an international investigation.