Today, three days before the scheduled opening reception, The Mattress Factory abruptly canceled Sites of Passage: Borders, Walls & Citizenship, a show meant as a cultural exchange between artists from Israel, Palestine and the U.S.

According to the museum, the exhibit was canceled because the three Palestinian artists — Bashar Alhroub, Manal Mahamid and Mohammed Mussalam — withdrew their participation.

A statement on the museum's website also read, "The Mattress Factory and guest curator Tavia La Follette would like to make a public apology to all Palestinians everywhere for the misunderstanding of this exhibition."

But the circumstances surrounding the cancellation — and the precise nature of the "misunderstanding" — remain unclear.

Another portion of the show was to take place at Pittsburgh Filmmakers' Filmmakers Galleries. As of 3:30 p.m. this afternoon, Filmmakers' website did not reflect the cancellation. But, somewhat confusingly, it did state: "As of May 25, 2014, the Israeli artists participating in the exhibit have withdrawn from the show." (The statement was subsequently revised to announce the cancellation.)

Reached by phone for comment, exhibit curator Tavia La Follette said only that the show was canceled due to "circumstances beyond our control. ... We had no choice but to close the exhibit."

Spokespersons at the Mattress Factory, which organized the largest portion of the exhibit, had not returned requests for comment at the time of this posting.

Asked whether the Palestinian artists — who had traveled to Pittsburgh for the show — wished to comment, La Follette said that they did not.

Possible clues about reasons for the cancellation might be found in additional verbiage on the Filmmakers web page about the exhibit. It read: "Correction: An exhibition description concerning 'Borders, Walls, and Citizenship' was prematurely posted without the agreement or prior knowledge of the artists involved. … All participating artists, and those that withdrew are against racism, against occupation, and in support of self-determination for Palestinians and all people. This show was never intended to be about normalization."

"Normalization" is a controversial topic in Israeli-Palestinian relations; the word refers to the idea that the two states can relate to each other like any two other states. Rejection of that concept has helped fuel activist groups including the Palestinian Campaign for the Academic and Cultural Boycott of Israel. On its website, the group defines normalization in this context as "the participation in any project, initiative or activity, in Palestine or internationally, that aims (implicitly or explicitly) to bring together Palestinians (and/or Arabs) and Israelis (people or institutions) without placing as its goal resistance to and exposure of the Israeli occupation and all forms of discrimination and oppression against the Palestinian people."

The Mattress Factory's April press release for the show didn't use the term "normalization." However, it did say, "The artists have been working collaboratively as part of a yearlong exchange that has allowed them to manipulate and respond to each other's work in ways that may be impossible to mimic in real life due to the physical boundaries of the countries of conflict they reside in."

The also release quotes La Follette saying, "A year ago, six Pittsburgh-based artists traveled to Israel and Palestine to research and meet the other artists. Now we bring artists from Palestine and Israel to gather together and create art here in Pittsburgh."

Ironically, given the apparent discord at work in the new exhibit's cancellation, the press release for Borders, Walls & Citizenship reads, "La Follette noted that the second exchange creates a similar type of visual discourse between [artists] from Israel, Palestine and the United States, in which the exhibit will take away political rhetoric and instead give a voice to the artists who live and work in those countries."

Pittsburgh-based artists in the show included Cynthia Croot, Andrew Ellis Johnson, Wendy Osher, Susanne Slavick and Hyla Willis. The Israeli artists were Itamar Jobani, Emmanuel Witzthum and Carnegie Mellon-based Dror Yaron.

Borders, Walls & Citizenship is part of the longer-running Sites of Passage project, the first of which involved U.S. and Egyptian artists, and was exhibited at the Mattress Factory in 2011.