(CNN) -- The U.S. military said it is investigating claims from Syria that U.S. helicopters based in Iraq killed eight people and wounded another Sunday in an attack inside Syria's territory Sunday. Syria's state news agency SANA said four U.S. helicopters crossed the border and struck a farm about 5 miles inside Syria before returning to Iraqi airspace. The raid occurred about 4:45 p.m. The helicopters hit a civilian building under construction on the farm, killing killing three men, the wife of a guard and four children, SANA said. Military officials are investigating the claims, Sgt. Brooke Murphy, a U.S....