Two U.S. Army helicopters crashed in southwest Baghdad late Saturday, killing two soldiers and injuring two others, the U.S. military said. The 1st Cavalry Division said the cause of the crashes, which occurred about 8:30 p.m., had not been determined. The aircraft went down in southwest Baghdad. Names of the dead and injured were withheld pending notification of relatives, but U.S. officials said they were assigned to Task Force Baghdad. The U.S. military has lost at least 27 helicopters in Iraq since May 2003, many of them to hostile fire, according to the Brookings Institution.