One supporter died of a heart attack and another was rushed to hospital during Borussia Dortmund's home match against Mainz on Sunday.
Dortmund claimed a routine 2-0 win thanks to goals from Marco Reus and Shinji Kagawa, but events at Signal Iduna Park were overshadowed by tragic events in the stands.
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Much of the game was played out in front of a subdued crowd as news of the heart attacks filtered through, with Dortmund confirming after the game: "There have been two tragic incidents inside the stadium during the game.