In the days after the terrorist attacks of Sept. 11, some workers and mourners at the World Trade Center site seized upon a cross-shaped steel beam found amid the rubble as a symbol of faith and hope.

For the past five years, the 17-foot-tall cross was displayed outside a nearby Catholic church. On Saturday it was moved again, to the site of the National September 11 Memorial and Museum, where it is to be in the permanent collection.

But the move quickly provoked a lawsuit from American Atheists, a nonprofit group based in New Jersey. It argued that because the cross is a religious symbol of Christianity and the museum is partly government financed and is on government property, the cross’s inclusion in the museum violates the United States Constitution and state civil rights law. The lawsuit, in turn, provoked the ire of the American Center for Law and Justice, a conservative public interest law firm, as well as others.

Now, the dispute over the “World Trade Center cross” is becoming the latest in a string of heated conflicts over how to memorialize the Sept. 11 attacks. It comes less than two months before the 10th anniversary of 9/11, and in the wake of a feverish debate over the construction of an Islamic cultural center and mosque within blocks of the trade center site.