A man with an Islamist background has been detained by German authorities investigating an attack on the Borussia Dortmund soccer team, the federal prosecutor's office says.
A Dortmund player and a police officer were injured when three roadside blasts were set off as the team headed to a Champions League game against Monaco on April 11.
Investigators searched the apartments of two suspects from Germany's "Islamist scene" and detained one of them, the prosecutor's office said in a statement.
It said metal strips had been used in the explosive devices set off in the attack, which injured one player and is being treated as having a "terrorist background."
The prosecutor's office said a decision would be made on whether to seek a judicial arrest warrant against the suspect. It did not say where the suspect was detained.
"The precise motive for the attack is unclear at present," it said, adding that police were still analyzing three identical letters discovered at the scene of the attack.
"No final analysis of the letter is yet available," federal prosecutor's office spokeswoman Frauke Koehler said.
A copy of a letter circulated earlier by national media showed it referring to a truck attack on a Berlin Christmas market that killed 12 people in December.
The Islamic State extremist group claimed responsibility for the Berlin attack, saying it had had been carried out by a "soldier" of the group.
Dortmund's Spanish defender Marc Bartra lays on the field during a game against Bayern Munich on April 8.
German Chancellor Angela Merkel was "horrified" by the Dortmund attack, her spokesman said.
"The chancellor was, like the people of Dortmund and millions of people everywhere, horrified by the news of the attack on the BVB team bus," spokesman Steffen Seibert told reporters on April 12.
He said that Merkel wished Borussia luck in their game later on April 12. The match was postponed as security was ratcheted up around Dortmund and in Munich, where Bayern Munich was playing Spanish team Real Madrid.
Security is among the issues at the center of Germany's parliamentary elections on September 24, a tight race in which Merkel is seeking to secure a fourth term.