Police and prosecutors in Germany say a letter addressed to Deutsche Bank chief Josef Ackermann was a fully-functional letter bomb.
Officials released a statement Thursday, but did not give additional details.
The bank's security personnel intercepted the letter Wednesday at the bank's headquarters in the city of Frankfurt.
The New York City Police Department said it had information on the incident and that the return address on the letter was the European Central Bank, which is the governing body for the 17-nation European currency.
Large banks in many countries have been put on alert. Anti-capitalist protesters around the world have been demonstrating against what they see as excesses of bankers and financiers. It was not immediately known who sent the letter which seemed to contain explosives.
Ackermann has headed Deutsche Bank since 2002 and plans to step down in May. Socialists have criticized the Swiss banker for his huge pay and for promoting high performance bonuses for bank managers.
Former Deutsche Bank CEO Alfred Herrhausen was killed by the left-wing terrorist organization the Red Army Faction in 1989.