Updated

Penn State University's administration published an open letter Thursday expressing their "deep disappointment" and  "dismay" over a campus sorority's decision to dress in Mexican costumes, which has been denounced by some as both racist and offensive.

"It has become clear that some Penn State students celebrated Halloween in costumes and in a manner that offended others and was contrary to many of the most important values our University seeks to advance among its constituents and in the world," read the letter signed by Penn State President Rodney A. Erikson, 18 trustees and other university staff.

Not only have they chosen to stereotype our culture with serapes and sombreros, but the insinuation about drug usage makes this image more offensive. Our country is plagued by a drug war ...which is nothing to be joked about

— Cesar Sanchez Lopez, PSU VP of Mexican American Student Association

"How any constituent groups or individuals in the University could behave with such insensitivity or unawareness is a question we must both ask and answer."

Penn State's Nu Gamma chapter of the Chi Omega sorority sparked controversy after posting a photo showing students dressed in ponchos, sombreros, fake mustaches and two signs that read: “Will mow lawn for weed + beer” and “I don’t cut grass, I smoke it.”

Some even had paint on their faces as to portray a darker skin tone.

"Costumes that include blackface, or that parody or imitate a person or groups of people, are always offensive to someone," the letter read. "They convey either a lack of awareness about the human condition and human sensitivities or, worse yet, disdain for the thoughts, feelings, histories and experiences of others. They suggest a failure to empathize or even a failure to think. They make all of us small."

The open letter does not outline any kind of punishment for the sorority and it remains unclear whether or not the university will act at all.

"These disturbing behaviors involved expressive rights protected under various federal and state laws -- rights which we strongly support, and which we honor by not vainly pursuing unlawful disciplinary action against the students involved," the letter read.

The sorority has apologized since the photo made its rounds on Tumblr Monday, according to the school newspaper "The Daily Collegiate."

"Our chapter of Chi Omega sincerely apologizes for portraying inappropriate and untrue stereotypes. The picture in question does not support any of Chi Omega’s values or reflect what the organization aspires to be," Jessica Riccardi, Nu Gamma chapter president, told "The Daily Collegiate."

Both the school's Panhellenic Council, which oversees Greek life on campus, and Chi Omega's national headquarters are investigating the situation.

"The Penn State Panhellenic Council recognizes the offensive nature of the photo and is therefore taking the matter very seriously,” the Panhellenic Council executive board said in a statement released Wednesday and obtained by the school paper. “We are addressing the situation immediately with the members of the chapter in conjunction with their national headquarters.”

The photo has also sparked controversy on Penn State's campus. Vice President of the Mexican American Student Association, Cesar Sanchez Lopez, told an independent Penn State blog called the Onward State that he was "disappointed."

“The Mexican American Student Association is disappointed in the attire chosen by this sorority. It in no way represents our culture," Lopez said in a statement. "Not only have they chosen to stereotype our culture with serapes and sombreros, but the insinuation about drug usage makes this image more offensive. Our country is plagued by a drug war that has led to the death of an estimated 50,000 people, which is nothing to be joked about.”

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