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. FULL POST