One of Canada’s most moderate and respected Muslim clerics was pulled off a plane Thursday and detained by U.S. immigration officials for 16 hours in Florida where he was traveling to deliver a Sept. 11 lecture warning against Muslim extremism.

The imam, Ahamad Kutty, was detained along with a second Toronto cleric Abdool Hamid. The Toronto Star reports the U.S. declared them a risk to national security.

40 Years Ago Today: Klan Bombing in Alabama Kills 4 Girls And 40 years ago today, four African-American girls were killed when the Ku Klux Klan set off a bomb inside the Sixteenth Street Baptist Church in Birmingham Alabama. The girls, Denise McNair, Addie Mae Collins, Carole Robertson and Cynthia Wesley were all between 11 and 14 years old.