Berlin (CNN) -- An Italian anarchist group has claimed responsibility for a failed mail bomb attack on Deutsche Bank CEO Josef Ackermann, German investigators said Thursday.
A suspicious package sent to Ackermann contained a functioning bomb, law enforcement officials in the state of Hesse said.
The package also contained a note from the Informal Federation of Anarchists, or FAI, the Frankfurt state prosecutor and Hesse investigators said in a statement.
The note mentioned "three explosions against banks, bankers, ticks and blood suckers," the officials said.
The letter raises the possibility that two other letter bombs were sent out to other institutions, the statement said.
The FAI an offshoot of the Italian Anarchist Federation. The group has claimed responsibility in previous years for failed mail bombs sent to some European embassies.
Formed in 1945, the Italian Anarchist Federation had seen "a slow but constant increase" of supporters in recent years, said the website of an umbrella group, L'International des Federations Anarchistes.
The Italian organization aims for "radical change" in support of "oppressed and exploited peoples," doing so with opposition to political powers and even the Catholic Church, the website said.
The package was intercepted Wednesday, said police in New York, whom the Germans alerted so they could step up security at Deutsche Bank offices in Manhattan.
The device, which contained shrapnel, was detected in the bank's mail room around 1 p.m. local time, said New York Deputy Police Commissioner Paul Browne.
It did not detonate.
"The return address was listed as a European central bank, which would likely increase the chances of him opening it," said Browne, who urged a general increase in mail room security.