Given the strength of the explosives, the suspect appeared to have sought to cripple the team, betting on a plunging share price that would have allowed him to sell at a substantial profit.

“He could have counted on a considerable fall in the value of the shares, when players had been seriously injured or killed” in the attack, prosecutors said, but they declined to name a specific figure, citing the continuing investigation.

Christian W. Röhl, a German financial investor and author, cited the 2006 James Bond film “Casino Royale,” in which the villain is a terrorist financier who seeks to destroy a plane in a short-selling bet against an airline company as an example for the suspect’s plan.

“If it had worked and the team had been hit hard enough that it would have been forced to withdraw from the match and from the tournament, or would have had to reorganize if five or six players had been injured over a long period of time or even killed, then most likely Borussia Dortmund shares could have plunged brutally,” he said. “Then, of course, there would be considerable gains to be made.”

The only player wounded was Marc Bartra, 26, a defender from Spain, who was hit by broken glass and sustained injuries to his right arm and wrist that required surgery, the team said. A police officer was also injured by the blasts.

The attack rattled Germans, coming a year after the country was struck by a series of violent acts by extremists pledging loyalty to the Islamic State, and targeting one of the country’s most successful and longstanding clubs for the de facto national sport.

Many were quick to attribute the attack to Islamic extremists, especially after three letters with identical content were found at the site calling for Germany to pull back from the Western military coalition against the Islamic State and by closing Ramstein Air Base, the main hub for American and NATO military forces in Germany.