One of the signs in the photo of Chi Omega sisters says "will mow lawn for weed + beer" and another reads "I don't cut grass I smoke it." The two women holding signs are wearing fake mustaches.
Chapter president Jessica Riccardi told campus newspaper The Daily Collegian that the sisters are sorry for "portraying inappropriate and untrue stereotypes."
The Penn State Panhellenic Council is investigating.
The Chi Omega national council says it is working on "educational directives" for the Penn State chapter and does not condone "personal degradation."