By Mark Hosenball WASHINGTON (Reuters) - A German defense official under investigation for alleged spying was in contact with a U.S. State Department officer rather than American intelligence agencies, raising questions about whether any espionage occurred, U.S. officials familiar with the case told Reuters on Friday. The officials, who are knowledgeable about the details of the case, said the U.S. government believes the relationship between the German defense official and his State Department contact was a friendship. If that is borne out by the on-going German investigation, it could help cool a crisis in U.S.-German security cooperation that has seen two Germans probed for spying for Washington and Germany's expulsion of the top U.S. intelligence official in Berlin. At the least, the investigation involving the German defense official appears murkier than the other, separate incident, which came earlier.