A letter bomb addressed to Deutsche Bank chief Josef Ackermann contained a fully functional bomb and was capable of exploding had it not been intercepted in the bank's mail room. The bomb was the work of a far-left Italian group, German authorities said Thursday; they added that more explosives may still be in the post.

The bomb was caught after a routine X-ray screening on Wednesday in the mailroom of the bank's Frankfurt headquarters, The Associated Press reported prosecutors and police from Hesse state saying in a joint statement.

Specialists from the Hesse Criminal Office working together with Frankfurt police have successfully deactivated the bomb, the statement said.

After an intensive search for evidence, authorities found a hidden, rolled up letter written in Italian.

The 'FAI - Federazione Anarchica Informale (Informal Anarchist Federation) claimed responsibility for the attempted letter bomb attack against Dr. Ackermann. The authors spoke of 'three explosions against banks, bankers, ticks and bloodsuckers.

According to media reports, Ackermann was not in the building at the time. Because of an ongoing investigation, the authorities declined to provide any further details on the matter.

The New York City Police Department has said the return address on the letter was the European Central Bank, which is the governing body for the 17-nation common European currency, the euro.

The Swiss-born Ackermann, 63, the face of capitalism in Germany, and who is one of the few senior managers in the country who is always surrounded by bodyguards, is due to retire in May, after more than 10 years on the job, Reuters reported.

On Wednesday, he was the recipient of  a negative prize by an anti-lobby group for allegedly cutting deals with German Chancellor Angela Merkel regarding efforts earlier this year to save Greece from bankruptcy -- charges rejected by Deutsche Bank.