Borussia Dortmund, one of Germany’s top soccer teams, was in the crosshairs of a series of explosions shortly before its scheduled Champions League match on Tuesday night.

Dortmund’s police chief, Gregor Lange, said late Tuesday night that the motive behind the “attack using serious explosives” is still unclear and that it remains to be seen whether it can be classified as a terrorist attack.

But two of the suspects in the attack may hold extremist views, Germany’s federal police said Wednesday in a news conference. Authorities found three letters at the site of the explosion, one of which alluded to foreign involvement in the Syrian war. One of the suspects has been arrested.

German Chancellor Angela Merkel was appalled by the attack, her spokesman Steffen Seibert said on Wednesday. “One can only be relieved that the consequences were not worse.”

Three explosions hit near the team’s tour bus a little after 7 p.m. local time while it was en route to compete against AS Monaco at the Dortmund stadium, according to a police report. Authorities said explosive devices were hidden near the exit of a hotel.

“According to what is currently known, the windows of the bus were smashed and one person was injured,” police said in a statement. “Currently there is no evidence of a threat to the visitors at the stadium.”

Borussia Dortmund said Marc Bartra, a 26-year-old defender from Spain, was hospitalized but is in stable condition after undergoing surgery that night to fix a broken radial bone in his arm and remove bits of debris lodged in his hand.

“We’re all in shock and our thoughts are with Marc,” team captain Marcel Schmelzer said, adding, “We hope that he will make a speedy recovery.”

Spanish Prime Minister Mariano Rajoy also tweeted his support for the player and wished him a speedy recovery.

The match has been rescheduled for Wednesday at 6:45 p.m. local time.

Police announced on Twitter that the rescheduled match will have heightened security. They also said authorities are investigating the authenticity of a letter discovered at the crime scene.

In a video posted online, Dortmund CEO Hans-Joachim Watzke said the team is “totally shocked,” but added that “it’s our task now to digest this somehow, because it’s only 24 hours before we have to play.”

In an interview with Swiss newspaper Blick, Dortmund goalie Roman Bürki recounted sitting beside Bartra on the bus when the explosion went off.

“After the bang, everyone in the bus got their heads down. We didn’t know whether there would be more,” he said. “The police arrived quickly [and] sealed everything off. We are all in shock.”

Wednesday morning, Bartra posted a picture on Instagram that showed his arm in bandages. “As you can see I am doing much better,” he said.

This story has been updated with information from Germany’s federal police, a statement from Angela Merkel’s spokesman and the status of Bartra.