The man, a German citizen, was taken into custody in Hanover Thursday morning after authorities received a tip, said the office's spokeswoman, Frauke Scheuten. She refused to identify the suspect or to give further details.
The office said Thursday evening that the man was released after being questioned by federal investigators, adding in a statement that they are still examining the case.
Scheuten said the man's apartment had been searched, but that so far no connection had been established to a terror cell based in Hamburg that included three of the suicide pilots in the Sept. 11 attacks on the United States.
"If the question is whether this person is supposed to have been involved in the Sept. 11 terror attacks, the answer is no," Scheuten said.
Three of the Sept. 11 hijackers lived in Hamburg, but only one arrest directly connected to the attacks has been made in Germany.
German police arrested a Moroccan man, Mounir El Motassadeq, at his Hamburg apartment in November on charges he controlled an account used to bankroll several of the Sept. 11 hijackers and had "intensive contacts" with the Hamburg terrorist cell. He remains in custody.
Germany has issued international arrest warrants for three other men believed to have helped plot the attacks before leaving the country Ramzi Binalshibh of Yemen, Said Bahaji, a German national, and Zakariya Essabar of Morocco.
German Interior Minister Otto Schily said recently police were following up some 20,000 leads into individuals and groups in the country believed to have links with al Qaeda.
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