Police said the incident was part of a targeted attack.
Investigators found near the scene a handwritten letter that claimed responsibility for the attack, prosecutor Sandra Luecke said.
One explosive device failed to go off, Luecke said.
Dortmund police Chief Gregor Lange said police have not ruled out any possible motives for the attack, which led to the match being postponed until Wednesday night.
Spanish defender Marc Bartra, 26, suffered injuries to an arm and hand, the team said.
Bartra, who has played 29 games in all competitions for the team this season, was treated at the scene and hospitalised.
The team later said Bartra was in surgery for a broken radius, a bone in the forearm and for “bits of debris lodged in…