Italian security forces failed to make arrangements for safe passage out of Iraq for a freed Italian reporter, whose car was fired on by U.S. troops, killing intelligence agent Nicola Calipari who brokered the reporter's release, according to an internal Pentagon memo. The memo says checkpoint soldiers are trained to deal with erratic speeding vehicles whose drivers ignored warnings -- a profile that matches the Army's version of events in Friday night's shooting. The memo says more than 500 American troops have been killed on the streets and at checkpoints in Iraq. Mistaken shootings of civilians resulted in "few deadly incidents" since the U.S. started checkpoints in March 2003, according to the memo. Meanwhile, the White House dismissed as "absurd" the stated suspicion of the reporter, Giuliana Sgrena, who said the United States tried to kill her because it opposes negotiations with terrorists to free hostages. Miss Sgrena, a reporter for the Italian communist newspaper Il Manifesto, provided no evidence. "It's absurd to make any such suggestion that our men and women in uniform would deliberately target innocent civilians," said White House spokesman Scott McClellan adding: "We regret this incident. We are going to fully investigate what exactly occurred." Maj. Gen. William G. Webster Jr., who heads the Army's 3rd Infantry Division, yesterday completed the "commander's preliminary inquiry." He has decided to conduct a more extensive inquiry, called a 15-6 for the regulation that authorizes it. Gen. Webster will name one officer to head the probe. A U.S. official said that of all the cars that passed through the checkpoint that night, the reporter's vehicle was the only one fired upon. "Something that car did caused the soldiers to fire," said the official, who asked not to be named. The shooting occurred at night at a checkpoint on a notoriously dangerous road that links Baghdad to the international airport. The incident has put a spotlight on "friendly fire" episodes that occur with some regularity in Iraq when motorists fail to heed warnings to stop at roadside checkpoints and are fired on by American troops who fear that the vehicle might be a weapon. Cars and trucks are a common weapon in suicide bombings and drive-by shootings. The soldiers did not know that Miss Sgrena and Italian agents were headed in their direction on the way to the airport for a flight back to Italy.