She said the explosives used in the attack contained metal pins - one of which buried itself into a headrest on the coach - adding it was lucky "nothing worse happened".
Three identical letters left at the scene of the blasts linked the attack to German involvement in the fight against Islamic State in Syria.
They mentioned the Berlin Christmas market attack carried out by an IS-inspired terrorist in 2016, according to the Sueddeutsche Zeitung newspaper.
The letters, reportedly written in German, began: "In the Name of Allah, Most Gracious, Most Merciful."
They also said sports stars and other prominent people "in Germany and other crusader nations" were on a "death list of the Islamic State".
The threat would last until German planes are withdrawn from the war zone, and the US airbase at Ramstein, near the French border, is closed. the letters added.
They were found near the team coach and their authenticity is being verified, as detectives have not ruled out the possibility that it might be a deliberate attempt by the attackers to mislead investigators.
A fourth letter, posted online, claiming responsibility which could have come from anti-fascists has been discounted by police following "serious doubts" over its authenticity.
SKY News.
