No suspicious letters found at U.S. military base after ricin alert WASHINGTON (Reuters) - A Pentagon spy agency said tests found no suspicious letters after an alert during a screening of incoming mail at a military base in Washington on Tuesday led a prominent senator to declare that the deadly poison ricin had been detected. Still, the Defense Intelligence Agency said the FBI took samples and would conduct further tests. It described the investigation as "ongoing." The United States is on edge following the Boston bombings last week and the discovery of letters laced with ricin addressed to President Barack Obama and Republican U.S. Senator Roger Wicker of Mississippi. The Mississippi man charged with sending the toxic letters was released from jail on bond on Tuesday, the U.S. Marshals Service said. Earlier on Tuesday, the DIA said initial tests indicated the presence "possible biological toxins." It said DIA security personnel detected a potentially harmful substance during routine screening of incoming mail at Joint Base Anacostia-Bolling in Washington, D.C. The DIA later made clear that did not mean any specific letter or package had been located. Adding to confusion during the day, Senate Majority Leader Harry Reid, asked about the release of the Mississippi man charged in last week's ricin letters to Obama and Wicker, said the latest incident involved the "same substance." It was unclear what information was provided to Reid. The DIA referred further queries on testing to the FBI. Reporting by Phil Stewart and David Lawder; Editing by Eric Beech