Stadium unrest before or during matches overshadowed three German Bundesliga football games over the weekend.
Several people were injured by a firecracker at a Bundesliga match in Augsburg in Germany's southeastern state of Bavaria on Saturday.
Augsburg's match against Hoffenheim ended in a 1-1 draw.
The firework was thrown from the Hoffenheim fan block. Police said that at least 11 people were hurt in the loud explosion.
Augsburg managing director Michael Ströll said that one person suffered blast trauma.
"One perpetrator is visible on video images," he said.
Ströll said that police were carrying out an investigation into the incident.
The local daily Augsburger Allgemeine reported that police had taken two suspects into custody.
The match was interrupted for around 5 minutes in the 57th minute over the firecracker explosion.
Hoffenheim sporting director Alexander Rosen also went to the Hoffenheim fan block immediately after the incident to calm supporters. Ströll said he paid a "huge compliment" to both Rosen and the referee.
"Unbelievable nonsense," Rosen said following the match, referring to the violent incident.
The firecracker incident comes a day after clashes between police and fans during the second-division game between St Pauli and Hanover on Friday evening.
Local police said on Saturday that 17 officers and 15 supporters had sustained injuries during the game, with pepper spray visibly used in the altercations.
Also on Saturday, police clashed with fans at Bochum's game with Cologne, and pepper spray was used.
Cologne's club said that there were problems with entry into the guest area, which resulted in police activity and injuries among fans. Bochum police said that Cologne supporters had wanted to "directly overrun" the guest entrance. A supporters' group instead complained on social media of an "excessive police action."
Police have launched investigations into cases of breaches of the peace, violations of the explosives laws and bodily harm.
sdi/msh (dpa, SID)