German police have confirmed that one person has been arrested as part of the investigation into a suspected terrorist attack on the Borussia Dortmund coach.
Frauke Kohler, a spokeswoman for the Bundeskriminalamt, also revealed that they were fortunate to not be dealing with any casualties after shrapnel was found lodged in other areas of the bus.
"These explosives contained metal shards - we can be happy that nothing worse happened.
"One of the metal shards in the explosive remained lodged in a seat headrest. It could have been worse.
"Two suspects are currently the subject of investigations. One person has been arrested.
"We are treating this incident as a terrorist attack," before adding, "an Islamic background is possible."
A letter recovered at the scene is being analysed for authenticity, but claims responsibility for the attack. It details Islamist motives, and invoked the Christmas market attack which also took place in Germany at the end of last year, blaming Germany’s military involvement in surveillance operations against Isis in Syria.
Investigators have since said the letter may have been an attempt to mislead authorities over the true identity of those behind the attack, according to Sueddeutsche Zeitung newspaper. The letter, written in German, is reported to have started with the words: "In the name of Allah, most gracious, most merciful."
A possible second letter from the anti-fascist scene claiming responsibility for the attack is also being examined by investigators, according to Focus Online magazine.
The explosions occurred shortly before the Champions League clash at Signal Iduna Park around 7.15pm on Tuesday night, smashing some of the vehicle’s windows and leaving Spanish defender Marc Bartra with an injury to his hand and arm. He later underwent surgery for a broken wrist.
A police officer, who had been travelling on a motorbike in front of the bus, was also injured. He is said to be suffering from blast trauma and shock.
Dortmund police spokesperson Sven Schönberg told BBC Radio4’s Today Programme that police “suppose that these explosive materials was hidden in the bushes near a street where the bus drove by,” and that investigators were working to verify the letter found at the scene.
He said the cancelled Champions League game will go ahead on Wednesday night with increased security planned to protect the teams and their fans.
Borussia Dortmund chief executive Hans-Joachim Watzke has also urged his players to show their club does not bend to "terror and hatred" in an emotional changing-room address.
Watzke admitted the bomb attack on the team bus which led to the postponement of their Champions League meeting with Monaco, and left defender Marc Bartra with a broken wrist, had left the team needing to come to terms with the "incomprehensible" very quickly.
And he said that when the team took to the Westfalenstadion pitch for the rearranged quarter-final first leg on Wednesday evening they would be playing "for everyone - no matter whether Borussia (Monchengladbach), Bayer (Leverkusen) or Schalke supporters".