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Multiple explosions went off near a bus carrying a German soccer team in Dortmund Tuesday evening, injuring a player ahead of a quarterfinal match, authorities and the team said.

Three blasts went off near the Borussia Dortmund team bus ahead at around 7 p.m. local time (1 p.m.ET) on Tuesday, ahead of the Champions League quarterfinal match against Monaco, police in Dortmund told NBC News.

The team said on Twitter that the blasts had gone off while the bus was at the team's hotel.

Dortmund Police Chief Gregor Lange said at a press conference late Tuesday that the incident was a targeted attack against the team, but the motive was currently unknown.

A prosecutor at the press conference said a letter was found near the crime, and its contents can be described as a "claim of responsibility." Authorities were working to determine the authenticity of the letter and would not comment further on what it said.

Police in Dortmund said they were working under the presumption that the incident was "an attack with serious explosives." They said they believe the explosives could have been hidden in a hedge near a parking lot.

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One person on the bus was injured and the windows on the bus were wholly or partially damaged, police said, adding they had no indication yet of what caused the explosions.

The damaged windows of the Borussia Dortmund's team bus following three explosions in Dortmund, Germany, on Tuesday, April 11, 2017. Stringer / EPA

Borussia Dortmund tweeted that center back Marc Bartra had been injured in the blast and was taken to a hospital. They did not reveal the nature of his injuries.

Dortmund chief executive Hans-Joachim Watzke later said in a video posted to the team's Facebook page that Bartra was injured in the arm and hand, "but the injuries are for sure not life threatening."

He added that the team was "completely shocked" and was now tasked with "coming to terms" with the incident.

A spokesperson for the team said at the press conference that Bartra was operated on for a broken bone in his arm and that some shrapnel needed to be removed. The team had spoken wit Bartra by phone, spokesperson added.

The first-leg of the match was postponed and was rescheduled to take place on Wednesday evening. Tickets for the game remained valid, the team said on Twitter.

Police Chief Lange said at the press conference that there would be a major police presence at the match.

The AP reported that a spokesperson at the already crowded stadium told fans of the match's cancellation, saying "there is no reason for panic here at the stadium."

Borussia Dortmund said on Twitter that they recommended people to stay inside the stadium and "remain clam to ensure an orderly departure."

The team also thanked their supporters for their understanding:

Thanks for your patience and understanding and the "Dortmund! Dortmund" chants, dear supporters of @AS_Monaco_EN! pic.twitter.com/Gcz9XGQY0J — Borussia Dortmund (@BVB) April 11, 2017

FIFA President Gianni Infantino said in a statement late Tuesday that the organization's thoughts were with "the people of Dortmund, and the fans of both Borussia Dortmund and Monaco following today’s troubling events."

"We are closely monitoring the condition of BVB’s Marc Bartra, and wish him a speedy recovery from his injuries," Infantino added.