German authorities say a piece of mail sent to Deutsche Bank chief Josef Ackermann was a fully functional letter bomb capable of exploding.
German prosecutors and police in Hesse state said in a joint statement that a suspicious letter addressed personally to Ackermann and intercepted at the mail room of the bank's Frankfurt headquarters on Wednesday "involved a fully functional letter bomb."
Authorities gave no further details Thursday, citing an ongoing investigation.
The New York Police Department warned local banks to bolster mailroom security Wednesday after the bomb was discovered.
Paul J. Browne, the NYPD's deputy commissioner of public information, told FoxNews.com that additional police officers were deployed to Deutsche Bank locations throughout the city to exercise "an abundance of caution," after the device, which was made of explosives and shrapnel, was found.
It was unclear where the package originated, but the construction of the device is evidence that it was not sophisticated, sources say. The bank would only confirm that a suspicious envelope was sent to the company and “the relevant unit of the bank informed the police.”
Ackermann has played a key role in resolving Europe’s financial crisis and has been an advisor to German Chancellor Angela Merkel.
U.S. officials said there are no strong leads, but named three possible scenarios, including Al Qaeda in the Arabian Peninsula, the group behind last year’s cargo printer bombs. Authorities are also looking into Iran’s recent threat to U.S. troops stationed in Germany. There is also a chance the package was sent by a lone wolf group.
Ackermann, along with other Deutsche Bank executives, are being investigated over alleged false testimony they gave during a major civil lawsuit in Germany, which raises additional questions about the origins of the package. Reuters reported that Ackermann is one of the few executives in Germany always surrounded by bodyguards.
Browne told the Associated Press that the European Central Bank -- the governing body for the 17-nation common European currency -- was listed as the return address. The ECB's headquarters are located two blocks away, across a park where the Occupy Frankfurt movement has pitched its tents.
Ackermann, 63, was awarded a negative prize on Wednesday by anti-lobby group Lobby Control -- based in the western city of Cologne. The bank chief was not present to accept the award that singled him out for allegedly cutting deals with German Chancellor Angela Merkel regarding efforts earlier this year to save Greece.
Deutsche Bank rejected the charges.
The Associated Press contributed to this report.