But prosecutor’s office says there is no evidence so far that Islamic State member played part in attack on football team’s bus

German prosecutors have said a man arrested after a bomb attack on a bus carrying the Borussia Dortmund football team is a member of Islamic State but there is so far no evidence he was involved in the incident.

The man, a 26-year-old Iraqi identified only as Abdul Beset al-O, arrived in Germany last year via Turkey, according to a statement from the prosecutor’s office.

The Borussia Dortmund (BVB) bus was hit by three explosions from pipe bombs as it drove from the team’s hotel to their home stadium in Dortmund on Tuesday night. Spanish defender Marc Bartra was injured by shrapnel, as was a police officer.

The Champions League match the team was due to play against AS Monaco was rescheduled and took place last night.

Abdul Beset al-O, who is believed to live in the western German city of Wuppertal, is due to appear before a judge on Friday morning as prosecutors seek to hold him for longer than 24 hours.

“The investigations have yet to result in any evidence that the suspect took part in the attack,” the prosecutor’s office said.

The statement said the man had been identified as an Isis member in Iraq, where he had led a 10-strong commando unit of fighters that had taken part in kidnappings, smuggling, killings and extortion. After his arrival in Germany, he is said to have maintained close contact with Isis members.

According to Spiegel, the man’s telephone was tapped by German intelligence, who just days ago monitored a conversation he had with an unknown person, who told him: “The explosive device is ready.”

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Investigators are also focusing on another man, a 28-year-old German identified as Abdullah Al Z, from Fröndenberg, 26 miles (42km) east of Dortmund. According to Spiegel, police reportedly entered his house on Wednesday when he was sleeping with his child. The man was said to be in possession of a BVB umbrella from the team hotel.

The pipe bombs used in the attack were set off by military detonators that had been detonated remotely, probably via a mobile phone, according to some media reports on Thursday.

Three identical letters printed on single sheets in German, found near the scene of the attack, point to an Islamist motive, but investigators have said they are not typical of Isis writings, not least because they make concrete demands.

The letter demands the withdrawal of German Tornado surveillance planes from Syria, where they are involved in the military operation against Isis, as well as the closure of Ramstein, the US military air base in Germany. It also states that, with immediate effect, “all unbelieving actors, singers, athletes and all prominent personalities in Germany and other crusader nations are on an Islamic State death list”.

Two other claims of responsibility have been made, by a group of radical leftists as well as a far-right sympathiser. Investigators have said they are keeping an open mind.

Play Video 2:27 Borussia Dortmund v Monaco Champions League fixture postponed after explosions – video report

But as pressure mounts on them to answer the question of who was behind the attack, which has deeply shocked Germany and led to a renewed debate about security in and around sporting and other events, criticism is growing over the decision to reschedule the Champions League match for less than 24 hours after the attack. Monaco won the game 3-2.

The strongest criticism for Uefa’s decision came from Thomas Tuchel, BVB’s head coach, who said the team had been informed via text message that they would play on Wednesday night, but no one had consulted him or the players beforehand.

“We had the feeling we were treated as if a beer can had hit our bus,” he said, adding he was made to “feel impotent” because he was not allowed to have any say in the matter.

“It was as if Uefa in their offices in Switzerland had come to the decision on their own,” he said. “I would have liked a few more days for the team.”

The European football body rejected the accusations, arguing the decision had been made jointly by BVB and AS Monaco on Tuesday evening.

Reinhard Rauball, the president of BVB, was also criticised for saying the team would deal with the trauma before he had apparently even spoken to them. “They are professionals,” he said. “I’m of the view that they can get over it.”

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Marcel Schmelzer, the captain of BVB, said that rather than spending the few hours before the match in the team’s hotel, he had been with his family, and had ignored their advice not to watch a press conference given by the federal prosecutor’s spokeswoman on Wednesday afternoon. “You just want to know what happened,” he said.

“I believe it would make it a tiny bit easier to deal with if we knew who was behind it,” Schmelzer added. He said that, on hearing from prosecutors that shrapnel from one of the bombs had penetrated the headrest of one of the bus seats, it had became clear to him “just how extraordinarily lucky we were. We’re all aware of that.”

He added that the team would have much preferred to have dealt with their trauma away from the pitch. “We would have been very, very, very happy, had [the match] been able to take place on another day,” he said. “Regardless of the importance of this competition, we’re only humans.”

Sokratis, a centre back for BVB, welled up as he thanked fans for their support after the game. He said later: “We were treated like animals, not like people.”

Another player, Nuri Şahin, told Norwegian television: “I don’t know whether people will understand or not, but until I went on to the pitch in the second half, I was not thinking of football.” Şahin was brought on after half-time.

“I know that football is important and I know that we earn a lot of money and have a privileged life. But we are also only people, and there is more to football in this world. That’s what we got to feel the night before last.”