Courtesy of a few seonds with Google, here is Here's a link to a State Department page with the relevant passage where they admit having passed on "incorrect" information. The incorrect infirmation is still carried in the rest of the page.

[November 10, 2005 note: We have learned that some of the information we were provided in the above paragraph is incorrect. White phosphorous shells, which produce smoke, were used in Fallujah not for illumination but for screening purposes, i.e., obscuring troop movements and, according to an article, "The Fight for Fallujah," in the March-April 2005 issue of Field Artillery magazine, "as a potent psychological weapon against the insurgents in trench lines and spider holes �." The article states that U.S. forces used white phosphorous rounds to flush out enemy fighters so that they could then be killed with high explosive rounds.]