The IDF's Judge Advocate General is investigating the alleged use of phosphorous shells during Operation Cast Lead in the Gaza Strip. The probe was launched at the instruction of Chief of General Staff Lt.-Gen. Gabi Ashkenazi and its findings will be released to the public. Several human rights groups have incorrectly claimed that shells the IDF fired into Gaza and which exploded in the air were phosphorus shells. The shells, fired by artillery batteries, were used to create smokescreens and contained phosphorus material, but were not actual phosphorus shells. A phosphorus shell is an incendiary weapon that lands on the ground and explodes, burning everything within a close radius. Each 155 mm artillery shell bursts, deploying 116 wedges packed with white phosphorus which ignite on contact with oxygen and can scatter, depending on the height at which it is burst (and wind conditions), over an area at least the size of a football pitch. In addition to the indiscriminate effect of air-bursting such a weapon, firing such shells as artillery exacerbates the likelihood that civilians will be affected. The use of such weaponry, the IDF said, is permitted under international law in open areas - to clear mines and roadside bombs - but is not permitted for use against civilians or in civilian areas. The IDF probe is checking whether the shells were used in civilian areas. Meanwhile Monday, Amnesty International delegates visited the Gaza Strip and claimed to have found indisputable evidence of widespread use of white phosphorus in densely populated residential areas in Gaza City and in the north. "Yesterday, we saw streets and alleyways littered with evidence of the use of white phosphorus, including still-burning wedges and the remnants of the shells and canisters fired by the Israeli army," said Christopher Cobb-Smith, a weapons expert who is in Gaza as part of a four-person Amnesty International fact-finding team. The smokescreen shells Cobb-Smith was referring to are not under investigation by the IDF, since their use is permitted under international law to cover tank and troops movements. Despite this, Cobb-Smith accused Israel of indiscriminate use of the shell which he called a "war crime." "Such extensive use of this weapon in Gaza's densely populated residential neighborhoods is inherently indiscriminate. Its repeated use in this manner, despite evidence of its indiscriminate effects and its toll on civilians, is a war crime," agreed Amnesty's Researcher on Israel and the Occupied Palestinian Territories, Donatella Rovera.