GAZA  In early January, a week into Israel’s war in Gaza, the home of Sabah Abu Halima was hit by an Israeli shell. Ms. Abu Halima, the matriarch of a farming family in the northern Gaza area of Beit Lahiya, was caught in an inferno that burned her husband and four of their nine children to death.

But as she lay in a bed on the third floor of an annex to Shifa Hospital in Gaza City on Wednesday, bandaged all over and in terrible pain, it was less the magnitude of her loss than the source of the fire that was drawing attention, not only from her doctors but also from human rights organizations and even the Israeli military.

Though there has been no independent confirmation, Palestinian officials say her family was hit by white phosphorus, a weapon that militaries use widely to obscure the battlefield but that is also limited under an international convention that bans targeting civilians with it.

The Israeli military issued a short statement on Wednesday, saying it was investigating whether its use of phosphorous weapons was improper and reiterating that it was “obligated to international law” in the matter. Early in the war, Israeli officials would not confirm whether the military was using white phosphorus at all, but said only that it was using weapons in legal ways.