One person has been detained in connection with the attack on the Borussia Dortmund football team bus, says a spokeswoman for the German federal prosecutor's office.
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German authorities are investigating an Islamist link after the targeted attack on the Borussia Dortmund team bus, dpa and other German media have learned on Wednesday.
Dpa, the Sueddeutsche Zeitung and networks WDR and NDR said a note claiming responsibility found at the site referred to the terrorist attack on the Christmas market in Berlin in December and the involvement of German fighter jets in the conflict in Syria.
Die Welt newspaper meanwhile said that Germany's federal prosecutor is now in charge of the investigation into the three explosions.
Police said earlier they are investigating in all areas, neither ruling out a terrorist background nor violent football fans.
Dortmund defender Marc Bartra and a policeman on a motorcycle riding ahead of the bus were injured in the explosions which came shortly after the team had departed for the Champions League quarter-final match against Monaco.
The game was rescheduled for later Wednesday. Also playing on the day were Bayern Munich against Real Madrid, with security measures for that game being reviewed by German police.