White House spokesman John Kirby stated on Monday that the United States is concerned about reports that Israel used white phosphorus weapons that were supplied by the United States in an attack in southern Lebanon in October.

We are aware of the reports. That is something to be concerned about. To try to find out a little bit more, we’ll be asking questions,” Kirby informed reporters on Air Force One.

Kirby said white phosphorus has a “legitimate military utility” for illumination and producing smoke to conceal movements.

“Obviously any time that we provide items like white phosphorous to another military, it is with the full expectation that it will be used in keeping with those legitimate purposes … and in keeping with the law of armed conflict,” he said.