Atheists have sued to prevent cross-shaped steel girders from the destroyed World Trade Center towers from being included in the official Sept. 11 memorial, saying the religious symbol is unconstitutional because its gives "preferential representation" to Christians who died in the 2001 terror attacks.

Workers found the broken, 17-foot-tall cross-shaped beams two days after the attacks, and they became known as the "World Trade Center cross." Saturday, the rusted cross was moved from its temporary home near St. Peter's Church and lowered into its permanent place inside the museum, which is under construction. A Catholic priest gave it a ceremonial blessing.

The lawsuit, filed Tuesday on behalf of four members of American Atheists, argues that including the Roman Christian-style cross at the National September 11th Memorial and Museum violates the First and Fourteenth amendments of the U.S. Constitution, as well as the New York State Constitution.

"Many of American Atheists' members have seen the cross, either in person or on television, and are being subjected to and injured in consequence of having a religious tradition not their own imposed upon them through the power of the state," the complaint (pdf) states. If the cross is not removed, the group wants a non-religious exhibit included.

According to the lawsuit, among the 2,792 people killed in the twin towers, 31 were Muslim Americans, approximately 400 to 500 were Jewish Americans, approximately 500 were non-religious Americans, and an unknown number were Americans of other faiths.

In a statement to ABCNews, the memorial foundation identified the cross as a "symbol of spiritual comfort for the thousands of recovery workers who toiled at ground zero," as well as an "authentic physical reminder" that "tell[s] the story of 9/11 in a way nothing else can."

In its press release, American Atheists notes, "No other religions or philosophies will be honored."

We love this country, and our constitution. We honor the dead and respect the families, which is why we will not allow the many Christians who died get preferential representation over the many non-Christians who suffered the same fate. This was an attack against America, not Christianity, and Christianity's does not deserve special placement just because the girders look like their religious symbol. We will pay for our own memorial of equal size inside the museum, or the museum will not include the cross. Equality is an all-or-nothing deal.

According to the complaint, two of the four plaintiffs were raised in "the Jewish tradition" and one has a "Catholic background." The fourth is the brother of a Marine reservist who did rescue work for two weeks after the attacks and died in 2005 of "weakened lung syndrome." He opposes a cross unless it is a Lutheran cross.