A man detained by police over a bomb attack on the Borussia Dortmund team bus is believed to have been an Islamic State fighter in Iraq.
The 26-year-old Iraqi has since been cleared of any involvement in Tuesday's attack - but police have kept him in custody following raids on two apartments.
He is believed to have led a 10-strong commando unit involved in killings, kidnappings, smuggling and extortion in Iraq.
Identified as Abdul Beset A, he arrived in Germany via Turkey in early 2016, the federal prosecutor's office said in a statement.
Following his appearance in court, a judge has approved an arrest warrant allowing investigators to detain him for longer.
Officers are still investigating three "serious explosive devices" which went off as the players and coaching staff left the L'Arrivee Hotel and Spa on the outskirts of Dortmund shortly before a Champions League match.
The explosives, which they believe may have been hidden in a hedge near the car park, contained metal pins and had a range of 100m.
One buried itself into a headrest on the coach.
Spain international Marc Bartra underwent surgery for a broken bone in his hand after being injured by shattered glass from the coach's windows. He has said he is "doing much better".
Prosecutors are also examining three identical letters claiming responsibility which were left at the scene of the blasts.
The letters, reportedly written in German, began: "In the Name of Allah, Most Gracious, Most Merciful."
They linked the attack to German involvement in the fight against Islamic State in Syria and also mentioned the Berlin Christmas market attack carried out by an IS-inspired terrorist in 2016.
They said sports stars and other prominent people "in Germany and other crusader nations" were on a "death list of the Islamic State".
The threat would last until German planes were withdrawn from the war zone and the US airbase at Ramstein, near the French border, was closed, the letters added.
They were found near the coach and their authenticity is being verified.
The team's rearranged Champions League quarter-final first leg at home against Monaco went ahead on Wednesday night and was won 2-3 by the visiting side.