By Moni Basu, CNN

(CNN) - Penn State has had its share of controversy for a while, but this week it is getting some more unwanted attention.

The university's Chi Omega sorority chapter is under investigation after a photo with Mexican stereotypes surfaced on a social media site.

It shows a group of sorority members dressed in ponchos and sombreros and wearing fake mustaches. One woman holds a sign that says: "Will mow lawn for weed + beer." Another sign says: "I don't cut grass. I smoke it."

The photograph was taken at a Mexican-themed party around Halloween, according to the independent college blog, Onward State. It was posted last week on Tumblr.

The university's Panhellenic Council said it had received concerns about the photo and that the council does not condone derogatory behavior from members.

"The Penn State Panhellenic Council recognizes the offensive nature of the photo and is therefore taking the matter very seriously," the executive board said in a statement.

"We are addressing the situation immediately with the members of the chapter in conjunction with their national headquarters," it said. "Our council and all its members strive to hold ourselves to a high standard and are disappointed by any failure to meet these expectations."

Jessica Riccardi, president of the Chi Omega chapter at Penn State, released an apology to The Daily Collegian newspaper.

“Our chapter of Chi Omega sincerely apologizes for portraying inappropriate and untrue stereotypes," she said. "The picture in question does not support any of Chi Omega’s values or reflect what the organization aspires to be."

The connections to the sorority were discovered through members' names tagged on Facebook, Onward State said. The posts have since been taken down.

Penn State public relations director Lisa Powers said that university officials have had conversations with Chi Omega members and that the women have expressed "deep remorse."

"The students in the photo are within their First Amendment rights to express themselves in this way, although we are certainly appalled that they would display this level of insensitivity and lack of judgment," Powers said.

"Because the right of free expression is guaranteed under the Constitution - for both behaviors we disagree with or for those that we support - we are approaching this as a teachable moment to engage this group of young women in discussions about their actions and to further educate them about diversity issues," she said.

Powers said the national leadership of Chi Omega will have to decide if disciplinary action is warranted.

A statement from Chi Omega headquarters said, "Personal degradation has no place in our organization, even if such behavior is meant facetiously or in jest. The Chi Omega national organization is taking this situation very seriously and is being thoughtful and deliberate regarding any sanctions or educational directives for the chapter."

At least one student at Penn State demanded a direct apology from Chi Omega to all Latinos.

"This is not a joke. This is our culture," said Ariel Coronel, president of the Penn State Latino Caucus.

She was shocked when she first saw the photo and said the signs the women were holding were especially offensive.

"There's a huge drug war going on in Mexico and you have a sign that says, 'We will mow lawns for weed and beer,' " Coronel said. "It's wrong on so many levels. How can you think this is OK?"

The reactions to the incident varied on Twitter. Here are two:

@ChiOmegaPSU The incredible amount of racism put into your "mexican" party was disgusting. —

Oscar Moises (@KidMacabre) December 04, 2012