The A5 envelope addressed personally to Ackermann, and with the return address marked as the Central European Bank, also in Frankfurt, was caught in a security X-ray screening because it contained wires and pieces of metal.
These are thought to have been what police described as an operational mechanism to set off the explosive powder contained in the envelope.
“The powder was not dynamite, either military or commercial,” a police spokesman said on Thursday. But he said that had the envelope been opened, the powder “could certainly have been dangerous.”
It could have burned the victim on hands, face and upper body, he said. “The aim was to hurt someone,” he said.
Tests on the powder were being conducted on Thursday, while an investigation was launched to find who had sent the package.
The incident caused alarm in New York, where a warning was sent to Wall Street companies to be particularly careful in handling packages.
A spokesman for the FBI told news agency Bloomberg, “The FBI investigation group for terrorism is working with the German authorities to investigate the incident in Frankfurt and identify possible threats against people or property.”
Ackermann, 63, has headed Deutsche Bank since 2002 and plans to step down in May 2012 after the group's annual shareholder meeting.
Financial sources have said he is being investigated by Munich prosecutors over allegedly false testimony he gave in a civil suit connected with the 2002 demise of the massive Kirch media group.