(CBS) — In the wake of the Orlando mass shooting, Muslim organizations in the Chicago area say they’ve reported to the FBI an emailed threat that came in Monday morning against a suburban mosque.

The email to the Islamic Center of Wheaton says: “Your tactics are well known by now.  You accommodate local opinion until you are large enough to overcome the locals. Then you strike.”

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The email says: “Americans fight back with a vengeance.”

Muslim leaders in Chicago say the Naperville mosque received a hostile phone call.

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Hani Atassi, a board member of the Mecca Center in Willowbrook, says they’re putting back a barrier they have just taken out.

“We actually took out the fence about two weeks ago. And just right after this happened, a lot of emails and a lot of fearful members of our community asked us to put back the fence,” he says.

“So we’re putting back the fence.  We’ve added more security. Obviously, a lot of people are concerned about this.”

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Muslim leaders in Chicago called a news conference to condemn the mass shooting in Orlando.