A letter bomb sent to Deutsche Bank chief Josef Ackermann was \"operational\" and could have exploded, German state police said Thursday after the envelope was intercepted. \"Preliminary investigations show it is an operational letter bomb,\" police in Hesse, the western state where Deutsche Bank\'s Frankfurt headquarters is located, said in a statement. The envelope addressed to Swiss-born Ackermann, CEO of Germany\'s biggest bank, arrived at Deutsche Bank\'s mailroom on Wednesday and was x-rayed after it raised suspicion among staff. \"Local police, working together with specialists from the Hesse state crime office, defused the explosive,\" the police said, adding that the investigation was continuing. The police said the Frankfurt prosecutor\'s office was working together with the Hesse state crime office (LKA) on the probe. An LKA spokesman called the letter bomb a \"dangerous explosive\" and said the authorities were in the dark as to who sent it. \"We cannot say anything at this point about the sender or any suspects,\" the spokesman told rolling news channel N24. \"There has been no claim of responsibility or information on a motive.\" A Deutsche Bank spokesman said he could not confirm media reports that the bank had stepped up security as a result of the incident. \"We cannot comment, for security reasons,\" he said. The case came amid mounting anger in Europe over the role of banks in the eurozone debt crisis and its impact on the economy at large. It revived memories of the assassination of Deutsche Bank chief Alfred Herrhausen on November 30, 1989 in a sophisticated roadside bombing mounted by the left-wing urban guerrilla group Red Army Faction. The 63-year-old Ackermann has been a divisive figure since he took the helm of the bank in 2002. He plans to step down in May 2012 after the group\'s annual shareholder meeting and will be replaced by the German-Indian duo of Juergen Fitschen and Anshu Jain. Ackermann said last month that he would not take a seat on its supervisory board next year as originally envisaged. He is under investigation by Munich prosecutors over his testimony in a civil suit connected with the 2002 demise of the media group of the late Leo Kirch but the bank indicated his decision to step aside was unrelated.