According to Newsday:

Several Muslim football fans claim they were profiled and unfairly detained by stadium security personnel and the FBI at Giants Stadium during a game in September when they were seen praying, alarming other fans who considered their behavior suspicious.

[The fans] were removed from their seats and questioned by security personnel after other fans saw them prostrating themselves on the ground as part of daily Muslim prayers....

[A]n FBI agent [allegedly] said they were being detained because someone had reported they were taking photos of the building, and asked if any of them had cameras. They said no, had their identification documents checked and were questioned for about a half-hour on topics including which mosques they attended, and where and how frequently they prayed....

[According to one of the Muslim men involved, they] were later told they could return to watch the game, but asked to sit in different seats.... They chose instead to leave....

UPDATE:

The New Jersey Sports and Exposition Authority said it will provide a special area for anyone who wants to pray at Giants Stadium [pictured] or the Continental Airlines Arena.

That's in response to Muslim groups' outcries after several fans who prayed at a New York Giants game were detained and questioned by the FBI in September.