One player was hospitalized, the team tweeted, but there were no details about his condition.
The team left its hotel about 7 p.m. local time (1 p.m. ET) for the UEFA Champions League quarterfinals match, a Dortmund police spokesman said.
Between 40 and 50 people, including the trainer and medical support staff, were on board when three explosions were heard, the spokesman said. The cause was unknown. The initial report was of one blast, but police later said there were three.
A preliminary investigation indicates the explosives “could have been hidden in a hedge near a parking lot,” according to an update posted on the Dortmund police website.
Twenty-six-year-old Spanish defender Marc Bartra was injured, the team said. Bartra has played 17 games in all competitions for Dortmund this season.
Video from the scene showed police escorting American midfielder Christian Pulisic away from the bus, apparently unharmed. Other images showed head coach Thomas Tuchel and members of the team in training gear, accompanied by police with long guns, standing on the side of the road. Some of the players looked stunned.
“Our task now is to process this because in less than 24 hours we need to play,” Dortmund CEO Hans-Joachim Watzke said, according to a CNN translation. “That’s our job. There is no alternative. It’s an unlucky situation but there is no other solution.”
The location of the blast was roughly 13 kilometers (8 miles) from Westfalenstadion, also known as Signal Iduna Park.
As news of the incident spread inside the stadium, fans of Dortmund’s opponent, AS Monaco, stood, clapped and chanted “Dortmund!”
No one inside was in danger, police said. Security was heavy after the explosions and the stadium was evacuated.
“Due to tonight’s incident, the UEFA Champions League match between Borussia Dortmund and AS Monaco has been postponed until Wednesday at 18:45CET,” UEFA, European soccer’s governing body, said in a statement. “This decision was made after a meeting held at the BVB Stadion Dortmund between UEFA, representatives of the two clubs and local authorities.”
CNN’s Nadine Schmidt, Atika Shubert, Steve Almasy and Sara Mazloumsaki contributed to this report.