On Tuesday, the DFB told ESPN FC it had begun proceedings. Under its rules, the club could face a fine or even a stadium closure.
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Hannover president Martin Kind has apologised for the racial abuse Mainz players Leon Balogun and Anthony Ujah were subjected to on Saturday.
Bayer Leverkusen missed out on the chance to go second in the Bundesliga as they were held 4-4 by Hannover in an eight-goal thriller.
Bayern Munich battled to a home victory over Hannover to move six points clear at the top of the Bundesliga.
Niclas Fullkrug's penalty ensured Hannover avoided suffering a third straight defeat as they clinched a 1-1 draw with Stuttgart.
Bundesliga leaders Borussia Dortmund suffered their second defeat of the season as Hannover won a thrilling contest 4-2 at the HDI-Arena.
Promoted Hannover defeated injury-hit Hamburg 2-0 at home in the "little northern derby" to maintain their fine start to the Bundesliga on Friday.
A former mainstay in the U.S. defense, Steve Cherundolo is now coaching Hannover's U-17s. He speaks with ESPN FC about his new role and much more.
Burnley's preseason friendly at home to Hannover has been abandoned on police advice.
Daniel Ginczek set up three goals and scored the fourth for Stuttgart as the 2007 Bundesliga champions finished with 69 points.
German second-division side Hannover have sacked their general manager and sporting director to make way for former Schalke GM Horst Heldt.
Borussia Dortmund beat Hertha Berlin on penalties to reach the DFB Pokal quarters for the sixth-straight year. Schalke and Frankfurt also advanced.
Werder Bremen hope to re-sign Per Mertesacker if Arsenal do not extend the defender's contract.
Per Mertesacker says he could return to Germany if Arsenal decide against renewing his contract at the end of the season.
Borussia Dortmund eased into the second round of the DFB Pokal with a comfortable 3-0 win at Eintracht Trier on Monday night.
Sevilla have signed Getafe playmaker Pablo Sarabia and agreed a move for Hannover's Japan midfielder Hiroshi Kiyotake.
The 27-year-old joins for an undisclosed fee and has put pen-to-paper on a four-year deal.
Travelling Wolfsburg fans threw flares onto the pitch in the derby at the Niedersachsenstadion, with one landing next to the home side's dugout.
Last month, Zieler said he would leave Hannover in the summer after they were relegated from the Bundesliga.
Bayern Munich celebrated their fourth straight Bundesliga title with a 3-1 win over Hannover in Pep Guardiola's last league game in charge.
Hannover have announced the death of Niklas Feierabend at the age of 19 following a car accident.
Ron-Robert Zieler has announced that he will leave relegated Hannover 96 in the summer.