The blast which rocked Borussia Dortmund's team bus ahead of their Champions League meeting with AS Monaco was allegedly caused by "explosive devices".
German publication Bild has broken the news, citing local police officer Gunnar Wortmann as its source.
Wortmann is quoted as saying that there were in fact three explosions near to the vehicle, which had its windows shattered during the incident.
An official police statement issued later in the evening appeared to confirm the report. "After our initial investigation we are working on the assumption that this was an attack with serious explosives," it read.
Spanish defender Marc Bartra was taken to hospital with what has been described as a "superficial" arm injury, but no other casualties have been reported.
The match was postponed as a result of the incident and is now provisionally due to take place at 5.45pm on Wednesday evening.
