A 28-year-old Moroccan man was arrested evening after being stopped during a routine identity check at Giessen railway station, north of Frankfurt.
His mobile phone was initially thought to contain the name of Khalid el Bakraoui, who Belgian officials say blew himself up at the Maalbeek metro station in Brussels, Berlin public broadcaster RBB reported, citing intelligence sources.
It has been reported that the arrested man was in fact exchanging messages with someone with a name spelt almost the same as Bakraoui's.
He remains in custody for other offences, according to the office of the German federal prosecutor responsible for terrorism cases, but is no longer suspected of links to the attacks.
Another man, a follower of the ultra-conservative Salafi strain of Islam, was arrested in the Düsseldorf region in western Germany on suspicion of links to one of the Bakraoui brothers.
A search of his house and workplace along with scrutiny of his mobile phone failed to produce any evidence tying him to the attacks in Belgium that killed 31 and injured 340, police told the DPA news agency.
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The man remains in detention pending further inquiries, police added.
"We so far have no tangible indication to suggest the two men have something to do with the Brussels attacks," said a spokeswoman for the prosecutor's office.